OpenTube

Try my free calculator and get ideal sub-frames. It's Online, Windows and Siril. #astrophotography

Deep Sky Detail

21,124 views

I made a sub-frame calculator for #astrophotography. It's available free online. as a Windows .exe or a SiriL python script.

online: https://deepskydetail.shinyapps.io/Su...
Windows: buymeacoffee.com/deepskydetail/e/524780
Siril: buymeacoffee.com/deepskydetail/e/524785

Correction: At about 18:08, after publishing the video I discovered a small bug in the calculator affecting the signal-based estimate in this example. After fixing it, the two minimum-sub estimates are actually much closer than shown here. The overall conclusion still holds, but the histogram and variance estimates are more consistent than the video suggests.

00:00 Introduction
01:12 Inconsistent Results?
02:13 The Theory
08:30 Using the Calculator
14:55 Interpreting the Histogram
19:35 Where to find it

Become a buymeacoffee member to help choose which products I review: https://www.buymeacoffee.com/deepskyd...

Affiliate Links:
High Point Scientific: https://www.highpointscientific.com/?...
Agena Astro: https://agenaastro.com/?rfsn=7802039....

Skywatcher HEQ5 Mount https://amzn.to/3NVrVQi
Skywatcher 80mm F7.5 Doublet https://amzn.to/47mbfZi
ZWO EFW mini filter wheel https://amzn.to/48OxhoN
Optolong LRGB Filter Set (1.25") https://amzn.to/47r23Tw
Orion 0.8x Reducer https://amzn.to/47s64a4
USB RJ45 Cable for Controlling Mount https://amzn.to/4aPlIzu
Raspberry Pi to control mount https://amzn.to/48mTBWH
R Pi case with touch screen https://amzn.to/3HvdNKl
ZWO Autofocuser https://amzn.to/3Skg0hX

ZWO 294MM Pro Camera: https://bit.ly/3tZmjOo
HEQ5 Mount: https://bit.ly/3O7VQVz (mine is Orion Sirius, which is equivalent)
ZWO Filter Wheel: https://bit.ly/3Soo5lw
Optolong Filters (LRGB, SII, Ha, OIII): https://bit.ly/3SlEPtJ (the Ha and OIII narrowband filters are better than what I have)
Skywatcher Evostar 80mm: https://bit.ly/4bfVjev (equivalent lens)
USB RJ45 Cable: https://bit.ly/48FRj50 (connects mount to laptop directly; mine is a different brand, but this should do)
ZWO Autofocuser: https://bit.ly/425XUDB
0.8x Reducer: https://bit.ly/3tQlbg7 (mine is Orion, but this should be equivalent)

Join this channel to get access to perks:
@deepskydetail

20 Comments

@deepskydetail Creator 6 months ago (edited) Pinned

How to get it:
Correction (18:18): A bug in the early version of the calculator caused the signal estimate to appear lower than it should. After fixing the bug, both estimates are much closer.
Online (file size is limited): https://deepskydetail.shinyapps.io/Sub_Length_Calc_DSD/
Windows: buymeacoffee.com/deepskydetail/e/524780
Siril: buymeacoffee.com/deepskydetail/e/524785

@on_wheels_80 6 months ago

IMHO the most decisive factors are: 1.: How many subs per hour are you willing to store, 2.: How likely is it that you need to throw away subs.

@Bekjeris21 6 months ago

Stellar work! Thanks

@GandalfderBlaue12 6 months ago

Thank you for the awsome tool. I'll make sure to try it out.❤

@precisionleadthrowing4628 2 months ago

brilliant tool and I just had a good play with it and in few moments it checks out really well with what I had to painfully figure out over months!

@TomBridle 5 months ago

Nice, i'm getting 99.9% efficiency

@Chimpy_Mc_Gibbon 6 months ago

This is the thing I think that people don't really get so with my rig which is a 8-in 600 mm Newtonian with a ratio of F3 imaging and bortle five to six skies. My read noise is overcome in approximately 10 to 15 seconds.

So the amount of signal I accumulate with exposures longer than this increases but so does the noise because of all the light pollution being sucked down by my telescope.

Ultimately that means if I expose for longer than 10 to 15 seconds, I'm actually decreasing the ratio of my signal to the noise, which means that the longer I expose after 10 to 15 seconds, the less that the signal from my deep space object contrasts with the background and so the lower the quality of the information I put into my stacking software.

Therefore, as you conclude, as long as you are making sure that everything you want to capture is above the level of the baseline noise of your camera, then you go for the shortest possible exposure that can achieve this and the only limiting factor with this is hard drive space and processing time during stacking.

I actually ended up doing what you're doing myself only about 2 or 3 weeks ago in order to optimise this.

@BlackforrestAstro 6 months ago

Windows exe works perfect, even on linux. Seems to run from a local webserver. Very clever 😃

@sonofoneintheuniverse 6 months ago

Testing for my own gear and environment. Here 30 sec subs are the sweet spot. Just like the Vera Rubin telescope... 😊

@BlackforrestAstro 6 months ago (edited)

Very nice. Thank you for your work. It would be nice to have a script for PixInsight too!

@MaggiesBirds 5 months ago

Very cool tool! I think the linearity mode of the QHY Minicam8 is messing it up a bit because it's giving me quite chaotic values, but it works great for my ASI2600

@mehensley1234 5 months ago

Thanks for the video and Calc. I would like to mention that I get different results with the same dark and light fit files between the online Calc and the Windows-downloadable Calc, using the same settings for bit depth, exposure, etc.

@richards3192 6 months ago

Interesting. Got it to run this time. I base my exposures on the calculated average ADU shown on the ASI Air Histogram for a sample sub. I know that i need to be around 300 ADU above the bias to have 10 x read noise swamp factor, so typically 60s luminance, 300s Ha. Your calculator is very close and gives my sample subs a 95%+ efficiency

@plane9182 6 months ago

Can you include image download time into the calculator? It's a small thing but my DSLR takes upto 6s to do a full cycle to take another image! Small but it definitely plays a factor with sub exposures as fast as 30s

@JethroXP 5 months ago (edited)

Minor Bug: The definition for the Histogram refers to a black vertical line (video does too) for the sky glow signal center, but the current version uses a white line (better UX IMHO).
Suggestion: I capture with NINA and it writes the Bit-depth, Sub-exposure length, and eGain in the FITS header, those can be read and pre-populated in the tool when the FITS file is loaded.
Question: Can you discuss how Narrowband filters impact these calculations? Assuming they simply make the minimum sub lengths longer?
Observation: Using an ASI2600 with an EdgeHD 8 at f/7 and 180s subs I'm getting a Min.Sub of 13.5s and a Min.Sub2 of 285.92s. Despite that at 180s my Measured.Swamp is 133.2746 and Sub.Efficiency is 99.63% so it seems the Min.Sub2 is less accurate.

@materialvision 5 months ago

Thanks for the tool! Now I wonder how much the bit depth really matters in all this? For my 585mm it is bit depth 12 but would upgrading to 14 or 16 bit really make any difference when it comes to noise or detail?

@Sharpless2 3 months ago

windows versions (both) dont work. Nothing happens after adding files.

@richards3192 6 months ago (edited)

Get a 'disconnected from server' every time I upload a sub.. 533 MM pro, not big files..

@GamerLudwig 6 months ago (edited)

i don't shoot with astro cameras
how do i figure out my gain from the iso value?
do i need a flat frame to calculate it? i have no idea . . .
edit: i found it for my 550d on photonstophotos. still no idea about my bridge camera though