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M27


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So... After installing an RA drive on my EQ5 I thought I'd attach my DSLR and give it a go with some AP. Quite some years ago I used to have an NEQ6 and used StarTools etc. The "lowly" EQ5 is not bad... I polar aligned it fairly quickly and tracking with the single RA drive seems to be very accurate.

Taken with the 80ED using APT with a Canon 70D.
ISO 800, 30 second exposures. No darks nor light frames :p (I seem the darks being important to get eliminate the internal DSLR noise or something. which may explain why I was battling with an horrendous amount of noise after stretching...)
80% of 21 frames stacked in DSS (I have forgotten everything here and going mostly by the recommendations in the software...)
StarTools - I have forgotten everything plus there's a whole bunch of new stuff since I last used it. (Completely lost!). Anyway, after clicking numerous random buttons I managed this...

 

M27_small.thumb.jpg.76dfd1c9fb3238fc5a1cc740ee43a645.jpg

 

 

 

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Perhaps you could try longer exposures (if your guiding accuracy pemits).

IIRC, he best ways to get rid of part of the noise is dithering between light frames (I don´t think it is possible without guiding), taking calibration frames (flats and bias for DSLRs) and increasing the integration time.

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29 minutes ago, barbulo said:

increasing the integration time.

I think this^ is the most important. Given your set up without guiding I would suggest 30 second exposures is probably about right. However, given the very low exposure time this is a good result.  M27 has quite a high surface brightness which certainly helps. If you have more time, you will be able to stretch the data a bit more without introducing too much noise.

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Many thanks for the suggestions.  I've got a feeling I may be able to just about squeeze 45-60 seconds unguided out of the mount but needs some experimentation.   Next time I'll shoot for at least 50+ light frames to get a decent integration time.  I've taken some dark frames at near enough the same temperature and also a bias set so once I've got some time, I'll go through it again and figure out StarTools properly... :)

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15 hours ago, Davesellars said:

I've taken some dark frames at near enough the same temperature and also a bias set

Don´t forget flat frames. For <1min subs they´re not very time-consuming but very effective.

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On 24/09/2022 at 22:52, Davesellars said:

Canon 70D.

Hi

Nice shot. 

To help with noise and other artefacts, don't use camera bias frames. Subtract instead a constant bias offset of 2048.

70d so lose the dark frames.

+1 for @barbulo's suggestion for including flat frames

StarTools: you've lost quite a bit of data. Go easy with second and subsequent AutoDev.

Otherwise, just keep adding to the frame count to make it even easier to process.

Cheers and HTH

Edited by alacant
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50 minutes ago, alacant said:

70d so lose the dark frames

Hi! Many thanks for the suggestion.  I always thought that dark frames were necessary - what is the reason for not needing them with the 70D - am I just adding further  noise?

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