My first proper DSO - M31

[frugal]

Despite the moon being very bright on Friday, I went out and took as many shots as I could of Andromeda. After taking twenty 120 second subs I thought I could stretch the AstroTrac a little more and I took another nine 300 second subs. First of all I stacked them in DSS, but then after reading the PixInsight tutorial that was posted recently, I have spent the whole weekend trying to learn PixInsight and how to integrate images in that.

I am not sure if the blurring is due to poor focussing, or if I have just reached the limits of the optics on a 100-300mm £70 zoom lens . It certainly seemed to be as tight a focus as I could get with BYE.

I am really hoping that it is clear at the end of the month, so I can go out and try again with a clear dark sky.

[Sandancer10]

Hi and well done for your first image. It sounds like you have the bug alright 

You can get sharper images if you get a Bahtinov Mask for the end of your scope. Just make sure you take it off once you have reached focus.

[Pete Presland]

thats a very nice image, i think the focus looks pretty good. there is a little false colour  on the edge of some of the stars and in the corners of the image the stars are out of shape, but i would guess thats probably the lens.

but it is a very good start and i hope you are pleased with it!

[frugal]

I have tried to make up a Bahtinov mask for the camera, but I am getting a large spike at 90 degrees to where the main spike should be, so it is hard to focus with it. I am currently using the FWHM setting in BYE and using BYE to step the focus one tick at a time.

I think I will need to try stopping the lens down a bit, however as it is already at f5.6 at 300mm that will restrict the light even more. I will try it on the next clear night and see if it cuts down the abberations.

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[Alien 13]

Nice work, the 1st image that pops out of the processing loop is always special and the bug bites hard after that.

Dont have any recomendations apart from looking around for any second hand old SLR M42 fitting prime lenses in the 135-200mm range with an adapter, not that the canon lens is bad but a bit more speed might help.

Alan

[frugal]

Alan, the speed is going to be a problem. If I stop the lens down a couple of stops it will be at f11 and I will need to expose for 4 times as long.

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[Alien 13]

Alan, the speed is going to be a problem. If I stop the lens down a couple of stops it will be at f11 and I will need to expose for 4 times as long.

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Have you tried it at other fl say 200mm you might not need to stop it down as much and you can allways crop the edges a little.

I can shoot with my old olympus lens wide open @ f3.5 if you factor in the camera crop value then its about 200mm equiv fl, it cost me £12 from a charity shop and £14 for the adapter.

Alan

[brettg40]

Nice image dude!

[frugal]

Alan,

I think my next imaging session is going to involve taking lots of sample shots of the same target with different f-stops and focal lengths to see what give the best result

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[frugal]

Interestingly this review site has a nice image comparison page where you can see test cards taken with the lens at different focal lengths and apertures.

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=288

I had also not realised that the lens was released 23 years ago! We bought it reconditioned when our previous Tamron lens died a few years ago.