M101 Galaxy

[nexusjeep]

Got another evening out in the observatory looking up at the heavens so had ago at M101 with the ASI2600 used the brain function and set the camera at the nearest to a calibration set I had so 200g / 20s exposures. Will probably not do that again as we captured 540 exposures and then used the best 75% ish percent so the image is 400 frames stacked. In the latest version of APP this took most of the afternoon to stack so will probably look to do a minimum length of 60s in the future if doing a long session.

No light pollution filter was used so this is straight from telescope to sensor.

Captured Frames Lights x 540, Darks x 50, Bias x100, Flats x100, Dark Flats x100

at 50mb per image they eat up disk space and APP had to allocate 180gb to build the integration image as temporary storage

Equipment
Avalon M-UNO Synscan Mount
Skywatcher ED72 Guide telescope + Altair 290MM Guide Cam + Sesto Senso focus motor
APM LZOS 130/780 + M/R 1x Flattener so F6 + ZWO EAF focus motor
ASI2600MC Pro Main Imaging Camera at 200g -10c Black level 12 20s exposures
Pegasus Ultimate Powerbox V2 to run everything.
Software SharpCap, Astro Pixel Processor, Photoshop CS2020

M101 400 x 20s integration time 8000s / 133m 20s Bortle 5 Sky 0% moon

_2020_03_24__M101_400x_20s__133m20s_200g_12bl_-10c by Nick Davis, on Flickr

Cheers
Nick

[turfpit]

Nick

Interesting write-up. The downside of the big megapixel camera is starting to show - significant time to process large files and high disk space consumption.

Your integration time was 133m. It would be interesting to see the outcome of 133x60s against the same object (and 65x120s) using the same gain and black level.

Dave

[nexusjeep]

Hi Dave,
Might well try that some time it would be interesting to see the difference, meant to also say in the write up this was without any light pollution filter in use so literally just telescope / camera so have added a note to the original post.

Cheers
Nick

[turfpit]

Nick

Think of that as a baseline. Now you will be able to evaluate the impact/benefit of the filter.

Dave

[umasscrew39]

Nice shot, Nick. Impressive with no filter although filters for galaxies aren't very useful. I've used UHC, IDAS LPS-D1, and CLS filters on galaxies over the years. I'm not impressed with any of them but most recently have been using the Optolong L-Pro which seems the best. I used it on M82 that I posted here recently (Bortle 6). Frankly, I would choose the L-Pro (maybe LPS-D1) or no filter as your color is nice. However, it would be interesting to see it with other filters for the sake of comparison.

Bruce

[oopfan]

Hi Nick,

Since you have a low-noise, CMOS camera the image quality won't improve dramatically from 20s to 60s but you will consume one-third the disk space, plus APP will complete faster.

Another thing you might want to try is selecting a ROI centered on M101 since it takes up so little real estate.

Brian

[mAnKiNd]

Nice one! Maybe try using the ROI function in Sharpcap to benefit, like Brian said?

Cheers
Minos

[BlackWikkett]

Nice image Nick! Pixel scale almost 1 to 1 with .97 arcsec / pixel. Curious have you completed a sensor analysis in SC? Would be nice to know what the "Brain" suggest for this camera / scope combo.

As to the filter discussion I have found using one shot color with out is futile unless you're in a true dark zone bortle 2 or less. I've tried various filters with the ZWO 294 and without. If you go no filter I'm constantly fighting gradients and or color shift. I've settled on the IDAS D1 in bortle 5 / 6 skies. Still can find gradients when imaging close to massive light domes like Atlanta but they're much less pronounced and more manageable.

-Chris

[nexusjeep]

Thanks for all the comments, at this point I am thinking of not using a light pollution filter as it does not appear to be overly causing an issue at the moment but will need to try a few more targets in different conditions.

Chris, I have run the sensor analysis which is were the 20s came from actually the exact brain calculation came out at 100g 17.4s 12 black level but I think from a post by Robin in the past SharpCap is skewed towards shorter exposures for the live stacking side which is not were I image I use the live stack to see what is building but actually process the image again via APP for the final project.

The other thing is that as the sensors get less noise in them it is going to take less and less exposure time for the light pollution to swamp this and subsequently possibly shorter exposures being calculated. In live stack I did have an issue when using the proposed timings as it had issues aligning the individual frames as the stars were very dim and as stated earlier in this post processing the number of images afterwards is a pain.

Brian, I tend to use the whole frame as I like the wider fields of view as it puts into perspective just how big it is up there and if I need a smaller shot I can always crop it if I need to as disk space and transfer speed is not an issue.

Cheers
Nick