bobro

Well if I can't find the target with the scope - put a wide angle lens on! 21 subs @ 120 secs with 135mm lens. Unfortunately didn't notice the camera display was on - some light from this registered on the sensor. It did show me how much brighter the image is with the lens at f4 when compared to my scope, so I think I'll do a comparative test to find out the real f# of the scope.

Art, are you aware that you can submit an image to nova.astrometry.net to identify where in the sky the image is? As I image from my back garden and have Internet access on my laptop, I take a quick snapshot and upload it as part of finding the target. You almost had the Pelican Nebula!

ISO setting may not do what you think (excuse me if you already understand this). The camera captures photons irrespective of the ISO setting. What the ISO setting does is enable amplification when the sensor is read. That is why a balance between the read noise and ISO setting is relevant - you want to keep read noise in the image as low as possible. So why not set the ISO to maximum? Well, to ensure bright parts of the image (stars) do not saturate and to leave room for stretching in software. So setting a high ISO value on a camera isn't necessarily a good thing - if I understand correctly (as always...). I understand you are going for high ISO as the exposures are short. That can help balance out read noise in faint detail, but won't help with the rest of the image.

Thanks Nige, I'm sure you are correct in that the southern part could provide more interesting imaging. A mosaic? That means I have to find it again - with accuracy of the area being imaged - aaarrrrghhh! I better get a goto upgrade!

The camera is set to ISO800 as I understand 400/800 helps to keep noise lower. It looks like longer exposure with my setup is still required.

Had another go at the NAN - without the UHC filter. A little better than my previous attempt, but I expected more nebulosity to show in the RAW image. 21 subs @ 360 secs.

Good to see the difference with longer exposure Nige - gives me motivation to have another go at the nebula with longer individual and total exposure.

So how did you achieve the colour change?

Believe it or not Neil, I was aiming for the Pelican but time was getting on so went for what I had as I couldn't get the final adjustment right! Yes, my captures don't seem to show the same number of stars as others achieve. It could be down to a number of things : 1) The OTA has been shortened by 40mm, possibly losing some light as the secondary is closer to the primary. Could also be light loss due to the focus tube being 1.25" and a long path up the tube due to the OTA being shorter and the camera relatively far out compared to scopes with shorter focusers. 2) The 1.25" Coma Corrector results in noticeable light loss and additional vignetting. 3) The UHC filter requiring longer exposure. You can see the difference in image brightness with and without the filter in the attached jpeg versions of raw images. Both are ISO800 240 secs and are of the NAN. As you say, guiding, together with the CC, are producing good round stars. What has also made a real difference is being able to very accurately polar align using SharpCap - DEC corrections are very infrequent when guiding. No issue with finding guide stars with the more sensitive camera which means the guide scope points in the same direction as the image scope - no field rotation (shouldn't be I know if PA is spot-on). I'm glad you posted your images of the NAN - lovely and sharp. Brings me on to something that puzzles me about filters and colour balance : If I try and do the usual lining up of RGB peaks after stacking to restore the colour balance following use of a UHC filter, will that not just result in degrading the image as some of the colour (especially green) will have been filtered out? Trying to achieve white stars would seem to be an issue. There must be a point I've missed about this type of filter..... Following your feedback, I think the next step will surely be longer exposures. I will try without the UHC filter first as it seems to be cutting out so much light. Bob

First attempt at (part of) the North American nebula. Didn't quite get focus. Tried a UHC filter - should this have helped with the image? Perhaps longer exposures would have been better as the subs were darker than normal due to the filter. Will try again to see if I can improve on it. 24 subs @ 240sec.

So just when I thought I was starting to understand something about imaging...... Well, to my untrained eye, the 10 sec subs have a tiny bit more detail and the 50 sec subs more noise. So that means the 10 sec subs win for me! As to why - no idea. Makes me wonder why I'm busy with guiding to obtain longer exposures. Perhaps it's a different story with exposures into minutes, though the short duration images (great composite) seem very good. Someone must be able to explain the result.......

Definitely interested Art - if I understand theory correctly both images should have the same overall signal/noise for the same total exposure time. However, the image with longer exposures should show more faint detail. No idea about theory regarding colour, though real images I have seen posted seem to lack colour with shorter exposures. It would help with a comparison if it's possible to use the same processing steps with both images. Bob

Glad you managed to fix it Nige - and the sky looks clear tonight! Bob

Great to see stars out last night - and for an extended period! First time I've managed to find M81 & M82 - thanks to nova.astrometry.net SharpCap polar alignment works very quickly with the new AR0130 camera - makes a real difference to guiding as DEC corrections are infrequent. 23 subs @ 240 secs - cropped.

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Nice capture! Although it's quite a blue target, I wonder if it's perhaps a little too blue? I'm interested in how people adjust colour balance - I usually just do it in DSS as I can't seem to successfully do it in GIMP alone.

No guiding with the new camera and DIY scope yet?

Until recently I used EOS Utility, but moved to APT (19 Euro) to allow dithering. In my limited experience I didn't have any problems with EOS Utility. A thought : enabling in-camera noise reduction results in an exposure doubling effect - could this be the problem? Bob

Kappa Sigma Clipping stacking in DSS can take care of planes, satellites, meteorites etc - see my post of April 27th on page : https://stargazerslounge.com/topic/279039-the-eq3-dso-challenge/?page=13

If you mean the focuser wobbles from side to side - I had the same problem and fixed it by putting self-adhesive ptfe strips on the inside of the outer focus tube. Focusing is now smooth but controlled and the camera weight doesn't make the inner tube move from side-side. The strips can be purchased from ebay for a few pounds and built up on top of each other to provide the required degree of control. HTH

Hi Graham. Looking forward to seeing your captures. Bob

Will do!

That's a question I don't know how to answer. If you look at the post in DIY Astronomer (https://stargazerslounge.com/topic/292376-low-cost-ar0130-guide-camera/) you will see that there looks to be some sort of automatic exposure control in operation that shows the brightest star but no more. OK for guiding but other types of imaging have different requirements. Can't say I understand what is happening yet - any suggestions will be helpful - have tried disabling auto exposure without any obvious change. Changing gain just seemed to make the main star darker.

Found the same module on Amazon here for £36.99. Great value! Just had to remove the lens and stick it to the bottom of a shortened Barlow Lens tube.

My new AR0130 guide camera module arrived earlier than expected, so decided to give it a go by imaging M3 - first time on this target and I was surprised how pretty it is. The guide camera worked very well - practically no need to move the guide scope to find a guide star, so I will post details under DIY Astronomer. M3 image (cropped): 13 subs at 300 secs. Kappa Sigma clipping stacking used again due to planes!