Location impact

The background light level is classified by Bortle level, and settles the maximum exposure time to achieve an IU value of around 50.  The Bortle level roughly relates to relative brightness. 

Brightness =  IU(8bit) * Lens  block  *  Filter block / ISO / exposure time

 Location           Bortle    Bkg 1/ISOsecs  Rel Bkg     B/Noise Sony      B/Noise QHY  cooled

Grand Tetons        1              0.006                  1                    5

Junction                  2-3          0.001-0.0028     3.3                 3

Wimberly                4             0.0033                5.5                2.5                  3.3 (low I)

Austin                      5             0.0036                6.0                                        5 

Line filter reduces intensity 180x, background 1.7x

Camera limitations 

Cameras             Type       Chip        Pixel   Pixel     ADC       Pixel      Diagonal  Tech(1).    Noise(2)  IU         Introduced  Backfocus

                                                           um                  bit        count       mm                         RT        -15C           

Nikon  1000      RGB       IMX206    1.2   4000      12          16M           5          EX            120                       2018

Sony 7a             RGB       IMX235    8.4   3600      14          12M         43          EX                5                        2014        18mm

QHY 183            Mono    IMX183    2.4   5339      12          20M        15           EX-R            4         1             2017        17.5mm 

Svbony 305       RGB       IMX290    2.9  1500       12            2M          6           EX-R                                                       11.5mm

Canon E mount                                                                                                                                                                    44mm

Pentax M42                                                                                                                                                                           45mm

(1) EX = Exmor.  EX-R  = Exmor - R.  Exmor R is a back-illuminated version of Sony's CMOS image sensor.[3] Exmor R was announced by Sony on 11 June 2008. Sony has newly developed a unique photo-diode structure and on-chip lens optimized for back-illuminated structures, that achieves a higher sensitivity of +6dB and a lower random noise of -2dB without light by reducing noise, dark current and defect pixels compared to the conventional front-illuminated structure, 8 dB translates to a 6x improvement. 

(2) Noise at around ISO3200 20sec exposure.  G30 on QHY = 3200 ISO.

Svbony Capture in SharpCap .FITS preferable to NINA. 

Gain in Sharp cap is 10x NINA  Gain 300 = ISO 3200. 


Save as RAW16  FITS format

PIPP -Debayer in 2 places YES , White balance YES BGGR pattern Output Split RGB NO 

Stack in Autostakkert  COO align

PS 3x resample.

Topaz OOF V blurry


Stack in DSS with FITS specified in load. Output as TIFF and you get full color image.

30 sec Dark has 4(8bit) FWHM noise - comparable to QHY which makes sense.  

Orion ED80 configurations   

400mm focal length 80mm aperture f6 lens 1.2 asecs resolution.

Focus assembly only works if focus adjust is horizontal and on bottom, with roller bearings on top. Works well with Alt/Az stage. On a GEM EQ stage, need to lock focus during moves and then rotate focus assembly BEFORE unlocking and refocus. 

400mm- focus 2cm    + Field F + T2 to NEX     + Sony7as            Camera limited resolution    400mm RGB   3.5 asecs/pix   unusable undersample

400mm- focus 5.2cm + Field F + 38mmT2      + Svb                     Diffraction/pixel match         400mm RGB   1.1 asecs/pix   undersample

400mm- focus 5.2cm + Field F + Filter wheel + QHY                    First line filter images           400mm HSL    1.1 asecs/pix

400mm-focus 4cm  + 2.5" to 1.5" + 1.5" to 5x + T2 to NEX  +  Sony7as                                      2000mm  RGB  0.8 asecs/pix  undersample

400mm-focus 1cm  + 2.5" to 1.5" + 1.5" to 5x +38mm T2   +  Svb                                               2000mm RGB   0.25 asecs/pix adequate sampling

400mm-focus 1cm  + 2.5" to 1.5" + 1.5" to 5x +85mm T2   +  Svb  (10x mag)                           4000mm RGB    0.12 asecs/pix  good sampling

Celestron 6 configurations

Check collimation 

To check collimation, place star in middle of field using eyepiece. Defocus and obstruction should be symmetric in the defocus ring. 

Move finger shadow to find mirror screw closest to narrowest ring, if in between use opposite screw 

Move star to edge of field in direction of narrowest ring. 

Adjust screw 1/6 of a turn to move star back to center of field. 

If to loose, tighten other two screws, if too tight loosen the other 2. 

Prime focus imaging  C6  0.7 asecs resolution

C6  + C6 to T2 converter + T2 to Sony E + Sony7as                                                                            1500mm RGB f10 1.0 asecs/pix  0.7x sample

C6  + C6 to T2 converter + 38mm T2 tube + QHY                                                                               1500mm HSO f10  0.35 asecs/pix  2x sample

C6  + C6 to T2 converter + T2 to C +Svbony                                                                                         1500mm RGB f10 0.35 asecs/pix

C6 to 1.25" converter + 1.25 to eyepiece + eyepiece 5x T2 + T2 to Sony E +Sony 7as                  7500mm RGB  0.2 asecs/pix     3.5x adequate sampling

C6 to 1.25" converter + 1.25 to eyepiece + eyepiece 5x T2 + T2 to C           +Svbony                     7500mm RGB 0.07asecs/pix 2amin field 10x good sampling 

RASA C6   with Hyperstar 6 V4 with filter  2 asecs resolution    Bf 39.8mm  M42

C6  +  Hyperstar M42 +  M42 to T2 + QHY                                                                                            300mm HSO f2   1.7 asecs/pix  sample OK for abb. limited 

C6  +  Hyperstar M42 +  M42 to C   +Svbony                                                                                        300mm RGB f2   1.7  asecs/pix 

Hyperstar collimation

Screws with white washers on HyperStar rotate camera as desired, tighten screws.

Long screws are PUSH, short are PULL. Push one, pull another see if collimation improves. 1/8 turn at a time.

Use cable tidy to id direction. 

System Performance 


Measured resolutions summarized below are consistent with these limitations.


Focal length Aperture  f number    Mount         Back Focus  Camera     Resolution      PIxel res

    mm                mm                                                   mm                          arcsecs       arcsecs

8mm                                 f3.5         Canon EF      44mm       Sony7as    120            250

20mm                               f2.0         Sony E           18mm       Sony7as      60            100

35mm                               f3.5         Pentax M42  44mm      Sony7as       40

100mm          50mm       f2.8         Sony E           18mm       Sony7as      14               20

100mm                             f2.0         Canon EF      44mm      QHY              20                6

300mm        150mm       f2.0         C6 RASA T2   55mm       QHY/Svb       2               1.7                  1.2x sample

400mm           60mm      f6.5         Pentax M42  44mm        Svb               2           

480mm           80mm      f7.0         Orion T2        55mm       QHY/Svb      1.1              1.4                 

539mm           70mm      f6.5                                Fixed         Nikon 1000  1.4              0.7       12amin        2.0x sample 6x pix digitization

1500mm       150mm      f10          C6      T2        55mm       QHY/Svb       0.7              0.4                           1.7x sample  observable pixellation

7500mm       150mm                      5x T2                                Svb               0.7              0.07      2amin         10x sample 

Measured resolution of Orion ED 80 -400 mm lens 0.8 arc secs edge resolution 0.14 pixel resolution, 1/2 Rayleigh resolution of 1.7 arc secs. 

Sony effective pixel resolution is 1.5 x actual due to RGB color pixels.



Photographing the Milky Way requires largest possible field and f number, a 20mm focal length f2 full field lens allows a full sky mosaic with around 40 images 94 degrees per field. A 20 sec untracked exposure at 2000 ISO on a astro mod camera images stars down to magnitude 10, and many nebulae.  A 8mm fisheye lens mirror compatible lens will allow filters  with a 2.5 um pixel camera (QHY or ASI), will give  50-75 degree field of view and enchanced color contrast Milky Way. 

Basic nebula = 30s ISO2000 with 5x to reduce noise. For low intensity nebula of whole MW add 3x  105s @ ISO6400, f/2. or 10x more exposure, needs v dark skies such as Grand Staircase Escalante NP and scanning stage for 20mm lens. 


The nebula within the Milky Way are some of the most visually interesting features with sizes from several degrees around Orion, to 10's of minutes.  The longest reasonably priced f2 refractive lens is 100 mm with an aperture of 60 mm and an abberation  limited resolution of 15 arcsecs.  Lenses are designed for a full frame sensor, most of which have insufficient pixel count to match the lens resolution.  Reduced field sensors (1/2 frame) can resolve closer to  the limit of the optics, so a nominal  "100 mm" f2 lens with 1/2 frame sensor has a field equivalent to a 200mm with 7 arc secs per pixel resolution. A larger (400 mm) focal length f2 telescope is available with a Schmidt Cassegrain telescope in Rowe Ackerman configuration where the secondary mirror is replaced by correction optics and imager so the focal length is solely determined by the main mirror. Resolution with the correction optics is 2 arcsecs, paired with 1/2 frame sensor.  Based on a 20 sec exposure, crude alignment to within 1 degree is fine.

Hubble palette 

Using HSO 8nm  line filters the intensity is 1/100 compared to RGB filters that have a 150 nm bandwidth.

Milky Way   8mm Canon mount with Canon-T2 filter adaptor and  QHY 

Nebula in context  100mm Canon mount  with with Canon-T2 filter adaptor and QHY 

Nebula close up C6 RASA  f2 lens combined with QHY cooled camera.


Gain 30 (6400ISO) and 200secs exposure gets to similar signals to Milky Way  reference conditions. An additional 10x in exposure time, requires 30 arc min (60 pixel) alignment to the pole star for tracking which  implies reasonably careful align.


C6 RASA f2 lens with Svbony camera has  using  1.5 degree field 70x20secs @ 6400ISO or equivalent good for Whirlpool, and Leo Triplet. Stars with magnitude 10 just resolved.  Most deep space objects  are relatively close to pole star axis and make align to axis less critical. RGB and Ha composite image makes for a really good look. Andromeda needs larger field QHY camera with RGB filters or 2 stitched Svbony  fields. 


The planets are much higher brightness and much smaller (20-40) arcsecs, so resolution is the key requirement.  

C6 Prime with Svbony, ideally with 5x to get lucky image oversample. 

For repeat exposure set autotimer = 2*exp time + 10 / delay 5

GEM stage implementation

For long exposures the telescope must scan in sync with the earth. The German EQ (GEM) stage has a Right Ascension axis that must be aligned with earths axis and a Declination axis at right angles. 

Polar align 

The RA axis is aligned the earths axis using a camera that is mounted to the RA. The RA is rotated to find the center of rotation. The camera is also used to find the earths rotation axis which is close to the pole star. The Altitude and Azimuth adjustment is use to align the stage axis to earths axis. 

The Polemaster camera is sold by QHY for the polar align process, with a 10 degree image field. A cell phone camera is a convenient way to place the polestar in the Polemaster field. A cell phone clamp is used to mount the cell phone to the stage. 

Polemaster process

Find polestar using cell phone camera  app

Center polestar in App window 11x9 degrees wide

Follow instructions to find stage center by moving polemaster mount. Start at -60 then 0 then +60 to eliminate any square error in Polemaster to RA axis. 

Check stage axis by lining up red icon and polestar - rotate polemaster arm - 10 polemaster pixel error = 2 arc min.

Check camera align by pointing at polestar and rotating camera theta. 

Align stage center to polestar (Rough align) within  4 arcmins - 0.01 arc secs/sec star drift 

Earths axis is 44 arc mins from polestar ( 1/3 of the way from polestar to lambda Ursa Minor. 

Align stage center to earth axis (Fine align red to green boxes) up to 30 arc secs (single pixel) - 0.001 arc secs/sec drift

AVX use model 


Mechanical : Telescope & cell finder mounted to AVX, plate to 400mm + SVBONY guide camera & Polaris finder mount.

Electrical: AVX Handset USB to lap top USB; Polemaster, QHY and SBONY to USB hub to lap top USB2. SBONY guide ST4 to AVX St4.

Power; Mount to Battery 12v, QHY cooler to Battery lighter.

Software :  CWI controls AVX mount, NINA controls QHY, PHD2 controls SVBONY & AVX guide, Polemaster controls Polemaster camera.

Align Components

Align guide and Polaris finder to Telescope using local reference.  Polaris is an option.

In a 2 degree field; Polaris, Rotation axis, stage axis all will be visible. Set tracking off, gain down, exposure long and create star trail. Then slew RA to see stage axis. 

Align to Stars

Use CWI.

1) Index

2) Star Above. Use phone to identify brightest star overhead. Use laser pointer to align telescope

3) Star near target - repeat. 

Use Cell phone to find target, then telescope, keep adding references closer to the target so the key pas works and the align gets better.

Align Stars - bright and directly above 


Arcturus in  Bootes

Spica  in Virgo 

Regulus in Leo 


Vega in Lys

Altair in Aquarius


Arcturus in  Bootes


Altair in Aquarius


Capella in Auriga 

Stephans quintet in Andromeda 


Sirius in Canis Major 

Capella in Auriga

Rigel in Orion

Procyon in Canis Minor

Pollox in Gemini

Betelgeuse in Orion

Aldebran in Taurus

Reboot PC, cycle mount, reconnect USB.  

Restart using Last Align so mount does not move.  

Check pole align 

To measure pole align errors, skip star align , and use QHY with PHD2 in "drift mode". 

Celestron PECTool for summing PEC runs. 

Mount design RA worm gear with period 480 secs or 8 min cycle, so need at least 24 mins to get a drift trend.

Nominal  PE stage performance +-15 asecs, improved to +-2 corrected.

Baseline test using 480mm lens 1.5 asecs/pix - 30 sec exposure with drift of 0.04 asecs/sec produces 1 pixel error.  5% of the worm cycle. This will be good enough with f2 RASA optics with 2 asecs resolution. 

To preselect section of worm gear, UTILITIES/MENU/RECORD/ENTER/ENTER - indexes the worm gear. Target will be somewhere in 2 degree window.

Position directly up - measure Az error using drift feature, northerly drift  = error west of pole.  Use for high accuracy cyclic RA worm error. 

Position to E or W  - measure Alt/tilt error using drift feature, northerly drift = error north of pole. 

Position on Polaris - pick edge star with 0.15 asecs/sec untracked error. and run for 24 mins  to measure  RA, PEC and scan rate error over 600 pix with 0.1 asecs/pix resolution with no DEC axis contribution.

Position directly up comparing 2 stars E and W of meridian. flipping RA and DEC sides. Collect images and find difference in RA for stars on equatorial - difference in RA is 2x orthogonality between RA and DEC.


Analysis of tracking errors gives an idea of underlying causes. Unguided, the DEC axis is fixed so after removing linear drift from pole align and orthogonality, the residual RMS or Standard Deviation is a quantitative measure of the combined seeing and star analysis errors, and their impact on spot size. In most cases seeing dominates, so "seeing limited" star spot size FHWM = 2x  RMS or standard deviation. In Austin in summer,  the estimated seeing  limited spot size = 0.9 asecs FWHM.


For my AVX stage with 400mm lens & Svbony camera , the contributions to unguided RA error over a 480 sec worm gear cycle  after careful Polemaster align are;

      Raw = 2.6 asecs RMS or  +- 8  asecs 3 sigma - consistent with specification

      Pole align error contribution = 9.6 asecs p-t-p

      Worm gear contribution = 3 asecs p-t-p

      Non random 10 sec exposure = 4.5 asec p-t-p  30-50 sec period

      After non-random  error removal = 0.72  asecs RMS 

      Seeing = 0.45 asecs RMS based on unguided DEC.

      Residual random position error =  0.55 asecs RMS - probably best that can be done !

The resulting uncorrectable spot size from random positioning errors with perfect seeing  = 1.1 asecs FWHM.

The most common solution is using a guide telescope to remove both pole align error and any systematic motion errors. Guiding programs such as PHD2 have measured sub pixel  noise ( 0.3 pixel RMS)  detection of star motion by following the shape of the image of a star.  Best performance guiding needs a guided telescope and camera with similar pixel and optical resolution to the imaging telescope and camera. 

For my AVX stage guided using 400mm lens with Svbony camera  with resolution of 2 asecs FWHM, over 480 sec, with  1 sec exposure.  

           RA raw error = 0.83 asecs RMS  random that produces a  star spot size =  1.6 asecs FWHM.

           Worm error = 0.3 asecs p-t-p

The guided raw error is slightly larger than the unguided random residual, suggesting that guiding may be over correcting on noise. Guiding corrects systematic errors, attempting to correct random errors will just increase total error. increasing exposure time will  tend to average out random position errors.

This also shows guiding within 2x of seeing RMS. The seeing error can be  reduced by increasing exposure time averaging out the seeing. A 4x increase in exposure should produce a 2x improvement in noise and guiding. Another strategy is to use multiple stars so that independent random variations in each star average out. Same rule should apply 4 stars should produce 2x noise reduction.   

For the AVX stage, the practical limit to best resolution in long exposures is probably FWHM of around 1-2 arc secs. A 30 sec unguided exposure has a good chance of matching guided. 

There are alternatives with improved RA accuracy, but their tracking performance is still  limited by the alignment to the earths rotation axis.  A dedicated RA scanning stage such as the Fornax Lightrack, uses a drive on the end of a long lever to achieve a RA tracking accuracy of +-1 arcsecs over 8 mins. It needs an additional RA & DEC axis  stage to point the telescope, so there is no star find capability.  A $5000 stage such a Fornax EQ mount has a claimed full cycle error of  +- 6 arc secs. The addition of a high accuracy encoder (Telescope Drive Master) can achieve +- 1-2 arc secs.  

Two modes; open loop (unguided) and guided. 

Unguided; if using CWI make sure that Siderial rate is 100%.

Residual error tests; hand controlled  0.04 asecs/sec, Supports 30 sec exposure with Orion ED 80 with QHY - 1 asecs/pix. 


Off axis guiding will not work for RASA f2 configuration.

On axis guiding - use the Orion ED, Pentax 400mm or 100mm lens  as a piggy back guide scope on the Celestron.  

Use a mono uncooled camera.  LH uses Orion 60mm guider 240 mm focal length  32 oz. 


400 mm pentax lens /  M42 to T2 / 20 mm T2 /T2 to C/ SVBONY SV305 Pro Telescope Camera, 2MP USB3.0 Astronomy Camera, 1.25 inch Astronomy Guiding Camera  2 degrees 2 asecs/pix.  - Mount to shared plate with Telescope.  Vixen bar to base of shared plate.  $89.00

100 mm lens - QHY as finder/guider 11 degrees, 7 asecs/pix.

Polemaster as a finder  11 degree field - 30 asecs res.

stage errors.jpg
Unguided ATX.jpg
Guided ATX.jpg

AXT test results  March 22 

Unguided 480 sec

Measurement DEC noise 0.45 asec RMS = 1/3 pixel

DEC was at neutral balance point showed 7 asec of backlash 

Drift 0.02 asec/sec  at limit for Polemaster 

Residual  RA RMS 2.6 asec 

RA PEC after 120 sec rolling average = 3 asec p-t-p, similar to pole drift, error is low when PEC is in opposite direction to pole drift. 

30 sec exposure RA 1 asec RMS - high res

120 sec exposure RA  2 asec RMS - f2 RASA PEC will help 

Unguided DEC

Error after linear = 0.45 asecs  - measures seeing and detection effects 

Unguided RA 

Error raw = 2.6 asecs RMS

Error after linear = 1.6 asecs RMS = +- 5 asecs 3 sigma

Worm contribution = 3 asecs p-t-p

Error after worm = 0.77 asecs RMS 

Subgroup 10 shows non random = 4.5 asec p-t-p  30-50 sec period

Error after sub 10 = 0.72  asecs RMS  - no obvious non randomness left.  

Contributions - Seeing 0.45 asecs RMS, random position 0.55 asecs RMS

Unguided 30 sec for high res (1 asec / pix), 120 sec for f2 RASA - add PEC

Guided 480 sec - 1 sec period.  

RA = 0.83 asecs RMS  mean zero - 1.6 asecs FWHM.

Subgroup 10 shows random variation (10 sec exposure) 

Worm contribution = 0.3 asecs p-t-p

Good enough for RASA and Galaxies.

At 1 sec exposure - 10x reduction in systematic, 15% increase in random. 

Need to increase the exposure time.  

Place DEC out of neutral balance to avoid backlash steps.

Make sure that camera axes match the RA - DEC directions... better calibration

in the case of standard deviation, the mean is removed out from observations, but in root mean square the mean is not removed. however in the case of noise where the mean is zero, the two concept are the same.

For 400mm lens aperture 70 mm aperture Dawes resolution = 0.7 asecs = FWHM  

Align results July 2022

C6 Hyperstar w. QHY 183 RT =  1.7 asecs/pix.  Drift = 0.1 asecs/sec or 30 sec unguided limit. Background G30 (3200 ISO), 6 sec exp, B = 61 IU(8)  FWHM = 4 IU(8). B/N = 15 & 1.4E-3 iso-1 sec-1. Smallest star FWHM = 3.4 asecs with poor (1.5 asecs dither) seeing and observable mis-collimation. 11Mag stars are saturated S/B = 4. Need to correct collimation. Basically performing to spec !

Fornax use model 

Fornax with  3 axis Manfrotto stage. R axis on RA plane. Tilt 1 provides DEC axis. Tilt 2 fixed at 90. 

Orthogonality error limits scanning to 0.1 asecs/sec. Accepting a 2 pixel scan error:

        100 mm lens and Sony 18 asecs/pix so up to 360 sec   

        100  mm lens and QHY   7 asecs/pix so up to 140 sec, sets limit for line filter imaging. 

         480 mm lens and Sony  4  asecs/pix so up to  80 sec, works fine with 30 sec max in the Sony.

Image processing

Milky way 3D.

Isolate nebula 

If needed remove stars from nebula - copy nebula, B&W, contrast to isolate stars in nebula, expand 2 pix, delete any stars that are part of nebula, make mask, shift nebula, copy from shift, paste into original nebula, blur to smooth. 

Make nebula transparent.

Make foreground stars - original image, contrast adjust to isolate a few bright stars, delete any associated with nebula. 

Deep Space look 

To create realistic deep sky images without blocking stars:

1) Copy master image - set 50% opaque - and move so that that stars pairs are distinct - set transparency 100% opaque.

2) On original - select stars using Astropanel/Astro/Hot pixel/Harder filter.

3) On filter - Create mask using magic wand - adjust tolerance  on background - Contract 1 pixel.

4) Copy filter on moved master to select local backgrounds to each star

5) Reorder layers so copied filter is added to original - Merge layers 

6) Select galaxies-feather - invert-Blur to eliminate residual variation

7)  Apply  levels by moving zero to obtain almost black background - do not overdo !

TARGETS - Whirlpool , Leo triplet 

Moon Composite 

Exposure 1/125 ISO 3200  PP7.  Continuous pics with hand controller - 40 or more frames. Lucky stack at 10%. 

Remove background - point / Tolerance 60 Feather 10 

HOS  filter image

Filter changer - 

1L/2S/3H/4O/5 clear

30s crude align 

120s needs fine align.

Calibration frames

Bias - readout noise - lens cap and short exposure

Dark - system noise - lens cap and same exposure time as lights (images)

Flats - vignette - white tee shirt over lap top screen.

Dark flats -noise on flat - lens cap with same exposure time as Flats

Collect at least 10 long exposures, with dark flats.  1/4 and 1/10 times for HDR.

Stack images in Deep Sky Stacker - group the different filters and exposure times, stack repeated images  using a common reference selected from best H image. Take non repeating images, use same reference frame, check images in turn and save. Use separate groups for different image sets that DO NOT include reference. 

In PS assemble HSL layers, change mode to RGB, align, equalize core color area, paste into RGB layers. reset black level, separately merge HDR color images, then merge color and L shorter exposure times.

Exposure times 

f2 30secs ISO2000 RGB is benchmark for good nebula =  

Filter increases exposure 500x, reduces bkg 6x.   

G30 is ISO 6000 so f2 240s G30 HOS should resolve M8. 

Example Rosette Nebula HOO image   f2  120secs x 4 frames per channel.  In Wimberly S/N  for Nebula 2.5:1, a 2x improvement with line filters for a M5.5 nebula, background 4 AU. Eagle nebula (pillars of creation M6.0 should increase exposure time to 200 secs. The nebula had a intensity of 10 AU, so darker Bortle or longer exposure for dimmer objects. 


Example Orion Nebula using 400mm f7 (1/10x) 120s G30 HOS filter = partial Orion nebula bkg 7, nebula edge 50. effectively 1/10 of full nebula. 4 deg field. 

Example Elephants Trunk Nebula M5.6   

Telescope: TEC-140 (F7)

Camera: SBIG ST-8300M

Mount: AP900 GTO

HA : 18x30 minutes (binned 1x1)

SII :18x30 minutes (binned 1x1)

OIII : 18x30 minutes (binned 1x1)

LRGB image

Useful for smaller galaxies (<1 degree) and excellent seeing using 400mm with QHY for resolution 1.4 asecs/pix. limited to 10 sec exposure time, 30 sec for moderate seeing. 

Align and stack multiple exposures in Deep Sky Stacker, set brightness at mid point. In PS, copy / paste RGB channels, adjust dark and mid point. Copy in L as new layer, change layer combine from Normal to Luminosity.

Sony7a astro mod without filter

Use curves - reduce white contrast - reduce red contrast - increase green slightly - reduce saturation. 


Use scanning stage to track and create a time lapse video. How to deal with transition in and out of totality.

Use Hyperlapse on phone to cover whole transition.   

Adobe PS 

Take multiple images- blend using mean to HDR

Sharpen by taking radial blur and subtracting original - do it twice.

Durkmiller technique

3.1. Pseudocode for MGN 1. Replace spurious negative pixels with zero or local mean/median.

2. Create Gaussian kernel of width wi . Kernel elements should sum to unity.

3. Convolve image with kernel to create local mean image B ⊗ kw.

4. Calculate difference between image and the local mean image, square the difference, and convolve with kernel. Square root the resulting image to give ‘local standard deviation’ image σw (Equation (2)).

5. Calculate normalized image Ci by subtracting the local mean image and dividing by the local standard deviation image (Equation (1)). Store the result.

6. Apply arctan transformation on Ci to give C 0 i .

7. Repeat 2-6 with the different kernel widths wi .

8. Take mean, or weighted mean if preferred, of the C 0 i to give a weighted mean locally-normalised image.

9. Calculate a global gamma-transformed image C 0 g by applying Equation (4).

10. Sum the weighted mean locally-normalised image with the global normalized image C 0 g , with appropriate weight h (as Equation (5)).

RosetteNebLayers32HOO Final Small.jpg
Elephants trunk.jpg
Jupiter close.jpg