My very humble attempt at M1

[Russell Archer]

Given the skill and artistry of others who've posted their beautiful images here (Jim, Bill, Erik, Dick, etc.) I hesitated a lot before posting the attached image

However, Jim was kind enough to take the time and trouble to provide me with some excellent practical advice a few months back.
And I promised to post my some of efforts, even though I'm all too aware they're very much 'beginner's standard'.

Anyway, here's my attempt at imaging M1 from a (very) suburban/light polluted site in London.

It's the result of around 3hrs 45mins total imaging over two recent nights (04 Feb: 9 x 300-secs Lum, 6 x 120-secs each RGB, 9 x 300-secs Ha; 07 Feb: 5 x 600-secs Lum, 5 x 600-secs Ha). The images were taken with a 12inch LX200 (plus f/6.3 focal reducer), SXVR-H9, and SX Lodestar auto-guider.

ACP 6 is performing beautifully for me. I still find it magical that ACP does what it does - I was able to sit and eat dinner with the family while keeping an eye on the images coming in via the ACP web interface running on my iPad. Geeky bliss

Russ

[Jim McMillan]

Russ, that's quite a nice effort!!!! You have no reason to hesitate to post. I'm very glad you did! I'd like to think some bit of my advice helped at least a little.

I'll be honest with you, one of the reasons I posted my "full moon NGC 3628" was with you and your bright skies in mind.

So, a little critique:

1) More exposure, lots more if possible. You'll find the SNR will improve a lot so you don't have to smooth/blacken the background as much. If you look at "the best" astroimagers, you'll find their backgrounds are a lot brighter than black.

2) Same goes for the DSO itself, lots more exposure. You've been able to tease a lot of detail in M1 - and you did it in such a way that it isn't "over-cooked." That's great! But, it's also fairly noisy. It takes an awful lot of exposure to get the dim detail reasonably smooth.

3) This advice assumings you're using a separate guide scope. If not, ignore it.

I'm guessing that 5 min sub-exposures is a reasonable trade-off between background levels and guiding accuracy. I suspect differential flexure starts to be problematic beyond 5 min. Perhaps longer works ok with Ha, but I'd watch what happens closely as you go beyond 5 min. The simple way to see if/how much differential flexure you have is to see how much each exposure "creeps". Any creep is due to differential flexure. If it "creeps" between exposures you can be sure it's "creeping" during the exposure, with the result being elongated stars. This, of course, is one of the key reasons why SBIG's internal guider system and/or an AOx device is such a good thing. There can be no differential flexure in those setups.

4) I've found Astronomy Tools (PhotoShop and PhotoShop Elements) to be an effective solution that allows the user to take advantage of the power of these sophisticated programs but doesn't require the user to understand them. Two functions I'd probably use on your image is to reduce the star size and increase the star color. (I'd also probably add spikes to the biggest stars because I just think it looks better that way.)

http://www.prodigitalsoftware.com/Products.html

Hope you find my comments useful.

Jim

[Russell Archer]

Hi Jim

Thanks so much for your comments. And thanks also for your "full moon NGC 3628" post.
The advice you gave me previously has been really helpful, and your specific comments on my M1 effort are very much appreciated

The M1 data (3hrs 45mins) is by far the most I've ever captured for any single target. As you say, I can very definitely see how the signal-to-noise ratio improves (a) with longer exposures, and (b) with "stacking" more individual exposures. Based on your comments in the NGC 3628/full moon post (e.g. around 11.5 hrs total imaging being a good maximum), as soon as we get a few more clear nights here in London I'm going to try and capture at least another 6-7 hours or so of data. I'll post the final image here.

I definitely take your point about the sky being too black. My lack of experience with Photoshop. As you say, I clearly overdid the use of curves to darken the background in an attempt to make the image less noisy.

I was pleased with the amount detail I was able to capture, with the LRGB filters giving a very different result to that through the H-Alpha filter. I then combined the two by setting the Ha image as a "luminance layer" on top of the LRGB image. I got the details of the technique from a book by Russell Croman. However, my Photoshop technique is very hit & miss ... I'm not always sure if what I'm doing is correct! So, on your suggestion I've purchased the Astronomy Tools Photoshop add-on. From my initial playing around it looks as if it'll be very helpful, so thank you for that!

Re the guide scope advice. I'm actually using an off-axis guider, which seems to work pretty well. I'm waiting on delivery of the Starlight Xpress AO unit, and I hope that will improve things substantially.

Anyway, thank you very much once again Jim for taking the time and trouble to pass on your advice and experience - I really do appreciate it a lot

Russ