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M81 with an Altair RC10


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I've been messing around on and off for a couple of years with an Altair Astro RC10 I bought from UK-ABS (replacing the focuser and backplate, remounting the primary in the cell and playing around with the collimation) but this is my first post of any images from the scope despite the files sitting on my hard drive for ages.

The first image contains only data from the RC10 (without a flattener) and a G3-16200 CCD (5h lum and Ha 1x1, 3h RGB 2x2, ) and was colour calibrated using the Pixinsight Photometric Colour Calibration module.

1793744135_RGBcombine_DBE_plusHa_colcal_stretchandsat_pluslum_quickprocmore_unsharp_darker2.thumb.jpg.016e28c7adc29814e299ccc5aab2570f.jpg

 

The second contains the same RC10 lum data but RGB and Ha data is a mix of some from the RC10 and the rest from my old C8 (using an Optec 0.5x reducer and atik 490EX CCD) totaling slightly more data overall albeit at a lower resolution. Colour was calibrated for the second image using the standard Pixinsight CC module.

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Although there's too much saturation (and slightly less fine detail) in the second image I think I prefer the colours even if the first image is supposedly more accurate. 

Grateful for any opinions/comments,

Paul

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I think both are magnificent, but the second image is the one for me as the stars are just a tad bit sharper/cleaner and the colour balance looks more vibrant. The first image looks to be a little biased on the greens to me so maybe a touch of the scnr tool in Pix?

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Thanks for your comments guys, a mixture of opinions on which version looks better. 

6 hours ago, morimarty said:

I think both are magnificent, but the second image is the one for me as the stars are just a tad bit sharper/cleaner and the colour balance looks more vibrant. The first image looks to be a little biased on the greens to me so maybe a touch of the scnr tool in Pix?

I've run the scnr green a few times during processing but I think the PCC has pushed it to a browner tinge. Also a few more blue subs went into the second image so blue signal probably a bit stronger there to start with. 

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Both are great images. I prefer the second image as the colours are certainly more vibrant and bringing out the blue is more akin to what I perceive to be the predominant colour of M81.

Steve

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Like the definition in the first image, and the colour in the second.

BTW, how do you find the coverage without a flattener? I'm still thinking of something similar, but a RC12 with a 16200 camera (Still not sure which yet).

Edited by DaveS
Blummin' autocorrect
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11 minutes ago, DaveS said:

Like the definition in the first image, and the colour in the second.

BTW, how do you find the coverage without a flattener? I'm still thinking of something similar, but a RC12 with a 16200 camera (Still not sure which yet).

Thanks Dave. There's a fair bit of distortion in the corners with this set up but overall the uncorrected field is surprisingly good. These images are substantially cropped but not entirely central crops due to position of appropriate  guide stars in the field. I'll try to remember to post an uncropped lum sub later. The quality of the stars across the same sized chip should be better in the 12 inch version.

I have a 2"TS rc flattener but not bothered to use it yet as i needed to get collimation sorted without it (and also is a hassle to fine tune the spacing). I also now have the small  riccardi reducer/flattener to try which gives a slightly less oversampled 0.75 arcsec per pixel along with correspondingly larger fov.

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1 hour ago, Allinthehead said:

Excellent images. Did you have any luck getting the Epsilon sorted?

Thanks Richard, no I haven't got round to sorting out the secondary recoating yet, been distracted by various things including deadlines for work and another telescope purchase of the refracting variety (on which I'll post something eventually...).

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6 hours ago, DaveS said:

Like the definition in the first image, and the colour in the second.

BTW, how do you find the coverage without a flattener? I'm still thinking of something similar, but a RC12 with a 16200 camera (Still not sure which yet).

Here's an integration and simple stretch of a dozen or so lum frames from the same imaging session (where I managed to guide keeping the target in the centre of the frame). You can see the off axis aberrations in the corners which the field flattener should take care of.

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integration_mosaic.thumb.jpg.f3bca78dd8451d2b59dfa867fb97aeb7.jpg

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Thanks for those crops, it looks like the 16200 is just a bit big for a RC without flattener. I note TS do two 2.5" flatteners, one for RC, and another for 'fracs. Might see if they're the same, as I have one on my triplet apo.

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5 minutes ago, DaveS said:

Thanks for those crops, it looks like the 16200 is just a bit big for a RC without flattener. I note TS do two 2.5" flatteners, one for RC, and another for 'fracs. Might see if they're the same, as I have one on my triplet apo.

When I bought the RC second hand it came with this corrector https://www.teleskop-express.de/shop/product_info.php/info/p2646_TS-Optics-PHOTOLINE-Full-Frame-APO-Corrector---Flattener-for-astrophotography.html (if I remember correctly) which is supposed to be very good for RC from reading around and looks the same as the one you're referring to. Unfortunately with my modified backplate/replacement TS focuser I didn't have enough in-focus when using it at the correct spacing distance. Instead I have this now https://www.teleskop-express.de/shop/product_info.php/info/p4006_TS-Optics-2--corrector-for-GSO-Ritchey-Chr-tiens-w-o-focal-reduction.html (and also this https://www.teleskop-express.de/shop/product_info.php/info/p5120_Riccardi-0-75x-APO-Reducer-and-Flattener-with-M63x1-Thread.html which I'm currently trying out with an Apo refractor), both are small enough to insert inside the 3" focuser drawtube so I can achieve focus ok with them, also they're big enough to avoid significant vignetting on the 16200 chip. Obviously this applies to my 10" RC so things might be different for a 12". Definitely handy if you can fit your corrector in the focuser though.

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My 2.5" flattener sits beyond the focuser, though I also have the 0.75x Riccardo reducer (Bought from Astrograph at Astrofest) and that sits inside.

I would also budget for a TS R&P focuser upgrade.

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