www.ukastroimaging.co.uk

Questions & Answers/Tips & Tricks => Newcomers Corner => Topic started by: Annie on 08:49:53, 08 February, 2018

Title: Tips for imaging star clusters please
Post by: Annie on 08:49:53, 08 February, 2018
I would like to have a go at imaging star clusters - perhaps the double cluster or M34 with DSLRs either  fullframe or crop frame, both unmodified and Takahashi 106ed (530mm fl, f/4.9).  I have read I need to do lots of 45-60sec exposures and was wondering what would be the minimum no of exps I  should aim for.  I would normally use ISO640 on my full frame  but there is nothing between ISO 400 and 800 with my crop sensor so would normally choose 800?

Thanks
Annie
Title: Re: Tips for imaging star clusters please
Post by: chris.bailey on 09:21:05, 08 February, 2018
Annie

Number one priority in my book as absolutely nailing focus! That includes watching the temperature and if it changes by much more than a degree, refocus again. Your Tak is quite temperature dependent so this becomes pretty vital. Shortish exposure yes but there are a lot of dimmer stars in the double cluster so I would experiment with slightly longer than 60 seconds, maybe 90. As with any DSO, the more subs the merrier and I would not hold back if you can get 100 90 second subs. As noise drops in quadrature, that will give you about 1/10th of the noise in a single sub exposure. Oh, did I mention FOCUS.

Processing them is, I'm afraid also quite key. Correct colour balancing to get reasonable saturation with believable (f not 100% accurate) star colour. Clusters are one object where I sometime play with G2V colour calibration i.e. calibrate to a know star colour but that is tricky, if not impossible, to do in Photoshop.

One more thing, FOCUS.

Chris
Title: Re: Tips for imaging star clusters please
Post by: Annie on 10:10:43, 08 February, 2018
Well Chris that sounds a good challenge!!

Annie
Title: Re: Tips for imaging star clusters please
Post by: blinky on 08:00:04, 17 February, 2018
I generally do around 3 min subs and the M44 image was only 9 of them, as has been said, focus is the main thing....https://blinkysastroblog.files.wordpress.com/2018/02/beehive-feb208.jpg
Title: Re: Tips for imaging star clusters please
Post by: Annie on 10:26:53, 17 February, 2018
Nice one Blinky.

Thanks for the tip!

Annie

TinyPortal © 2005-2012