Live Stacks 8-29 through 8-31 2019

[BlackWikkett]

Finally clear skies after weeks of cloudy nights! Thought I'd switch it up and put my Stellarvue 70mm into service. The goal was to capture some of the larger objects and leverage SharpCap's Live Stack feature. Here are some of the highlights from two very long nights. Captured over 20 objects you can seem them all at https://www.flickr.com/gp/165305863@N04/95G6j3

Equipment:
Stellarvue 70mm f/4.8 336 FL IDAS D1 LPS (using .8 focal reducer / flatner)
ZWO ASI294MC Pro Cooler at -10c
iOptron CEM60 mount
SharpCap 3.2.6086 (64bit)
PHD2 (first night no guiding)

Most stacks are using 30 second subs at 300 gain 9 brightness. Using 25 sub master dark and 50 sub master flat. SharpCap live stack enhancement with Gaussian blur and unsharp mask. Final live stack processed with Photoshop for crop, background and color balance and noise reduction. My skies are Bortle 5 and pushing into Bortle 6.

Image were capture during live broadcast at https://www.nightskiesnetwork.com/

You can following the link for any image to see more details.

M8 M20 PS Edit Stack_43frames_1290s_WithDisplayStretch by Black Wikkett, on Flickr

NGC6559 IC5070 PS Edit Stack_51frames_1530s_WithDisplayStretch by Black Wikkett, on Flickr

NGC6992 NGC6960 PS Edit Stack_70frames_2100s_WithDisplayStretch by Black Wikkett, on Flickr

IC1805 IC1795 PS Edit Stack_60frames_1800s_WithDisplayStretch by Black Wikkett, on Flickr

M45 PS Edit Stack_70frames_2100s_WithDisplayStretch by Black Wikkett, on Flickr

M31 PS Edit Stack_122frames_3660s_WithDisplayStretch by Black Wikkett, on Flickr

IC1396 PS Edit Stack_294frames_8820s_WithDisplayStretch by Black Wikkett, on Flickr

M42 + M42 Core Blend PS Edit Stack_75frames_485s_WithDisplayStretch by Black Wikkett, on Flickr

[turfpit]

Wickett

That is 2 well disciplined imagining sessions. All looking good. You must have been near sunrise to capture M42? Congratulations.

What is gain 300 as a % of max gain on that camera?

Dave

[nexusjeep]

Impressive set of images well done , I would dearly love two nights in a row to be clear at the moment as the weather has been awful.

Cheers
Nick

[umasscrew39]

Excellent images- great color and star shape. I always like the wide FOV shots even if cropped a little. I've not gone any higher than 4 with brightness - may have to experiment more with this as I am also Bortle 5 pushing 6 skies. However, horrible weather for a month in Orlando and hoping Hurricane Dorian misses us. I had hurricane straps installed on my 20ft Pier Tech split sliding roof to my observatory, so they better hold or I lose everything.

[BlackWikkett]

Thanks all for your kind words!

Wickett

You must have been near sunrise to capture M42? Congratulations.

What is gain 300 as a % of max gain on that camera?

Dave

Sunrise was at 7:09 AM and the main M42 subs were captured at 15 seconds at 5:40 AM. The M42 core images were at 6.48 seconds at 6:14 AM. Really had to adjust the Live Stacking color balance as the pre-sunrise sky glow was taking it's tole. Used a Photoshop layer mask to combine the images.

The ASI294 unity gain is 120 that gives about 13 stops of dynamic range but at the expense of longer exposures. At 300 gain the camera still attains over 10 stops of dynamic range. Max gain on the SC scale is 550 but the data sheet from ZWO only goes to 400 gain with still gives 9 stops of dynamic range. This wide dynamic range along with 63700e full well makes for a very flexible camera. The 294 is by far my favorite for the type of imaging I do which is mainly live stacking and broadcasting on NSN. All this prattling on and the answer to the question is about 60% if you look at it as a liner scale.

I've not gone any higher than 4 with brightness - may have to experiment more with this as I am also Bortle 5 pushing 6 skies.

The way I determine the brightness (offset) value is to capture an image at the exposure and gain settings I intend to use. Since I've had plenty of the experience with the scope and camera combinations I have this is fairly easy to arrive at. While taking the exposure I'll have the Smart Histogram open and watch that the peaks of the histogram fall into the green range and that the range is off of the left edge of the histogram. I'll increase the brightness value to move the peaks without adjusting gain or exposure. These values will of course be different for scope, camera, filter and sky condition combinations.

Come over to NSN and check out folks broadcasting their astronomy journey. You'll find many users of SharpCap that are live stacking. Live audio and text communication and the broadcasters are more than happy to answer questions. We're constantly trying new techniques and discuss our shared hobby. Hope to see you all there!

[umasscrew39]

Thanks for the updates. Agree- the 294 is an excellent camera. I am very familiar with FB NSN- I post on there a lot. Very nice site and lots of images with SC. For me what seems to work best is combining SC live views and then export the stacks to PI for some post-processing.

[turfpit]

Wikkett

60% gain - thanks for that. Fits nicely with this viewtopic.php?t=561 using 74% gain and 30s exposures. The message I get is 30s exposures and > 50% gain looks like a good starting point for me to experiment with Live Stack. I am aware the cooled camera helps with the higher gain settings.

Having studied your original post more closely, you are consistently obtaining a good return on 35m of capture effort for a target.

For setting offset/brightness/black_level (depending on camera manufacturer) I have settled on this - for a given gain, capture a single bias frame and inspect in FITS Liberator looking for a centralised histogram (definitely not clipping the left or right axes). Adjust offset/brightness/black_level and repeat to find the smallest value that gives the histogram condition described. At least it is a systematic, repeatable process which has given me satisfactory results.

With Orion this time around I am going to try for a mosaic from M42 up to to Alnitak - end of September onwards I think.

Dave

[BlackWikkett]

Word of caution on brightness, red and blue settings in SC image controls on the left side camera control panel. If you intend to use a master dark and master flat while live stacking in SC. These rules have proven to make for successful live stack images. Use this for creating the masters in with SC. This is for one shot color and I've used this for ASI183 , ASI224, and ASI294. I suspect it will work for any one shot color camera.

1. FLATS: Use 50 for red and blue color balance and 0 brightness.
2. DARKS: Use the same brightness and color balance settings that you'll use for lights