x6gas

Nothing wrong with the CEM60 at all - very far from it, it's a terrific mount (though the CNC machined finish of the CEM40 is a bit step up astatically). However, the plan is that the CEM60 will be more or less permanently mounted on my pier and the 40 will be a grab and go field mount for some dark sky trips (sadly I've never really got on with my astrotrac, though of course that's a very different animal.

One of my favourite targets and you've done a terrific job...

I bought an iOptron CEM40 mount back in May... there was a bit of a production issue with the first one so Nick at Altair Astro had to source me a replacement (he was great, as ever, by the way) but that took a while... Once it arrived I tried imaging M13 to add to my Messier images and as a shakedown for the mount but a problem with my filter wheel meant that I collected a LOT of one channel so I didn't really have anything to post... and then cloud, and work, and cloud. Long story short, this weekend has been the first in a long time where I've been able to capture some data. First and foremost, I have to say the mount is outstanding. It guided for two nights solid without missing a beat. Admittedly I had to trash the first night's data because my focus was off but was getting 2 arcsec p-2-p and 0.5-0.6 arcsec RMS... I don't have great seeing and this was with PHD settings straight out of the box (similar results for hysteresis and predictive PEC). PHD was also reporting pretty poor polar alignment (long story regarding my new peer for another time). Now funny story: I'm still learning Pixinsight and have been having trouble calibrating my lights and during the processing I completely forgot to align the light frames; I missed that step and just stacked them and, honestly, the stars were pretty much as round as the properly aligned stack which really brought home how good the guiding was over the whole session. Anyway, here's the result preprocessing in 'ole faithful AstroArt with a quick stretch in PS5. Scope: Tak FSQ85; Mount: iOptron CEM40; Camera: Atik 460ex; Filters: Astrodon; Guiding: Atik OAG/PHD2 38 x 600s Ha for a total integration time of 6 hours 20 minutes. OK it won't win any awards but I think it demonstrates that this mount has real potential. The CEM40 ia also a lovely looking thing - sadly my CEM60 is a bit of an ugly duckling (though it too performs well).

Lovely image mate. You managed to get some lovely blues and gold in there...

My CEM40 finally arrived last week (long story) and it's due to be clear tomorrow. I want to run it with my baby Q first but I hope to test my TS130 frac on it; not that I really plan to use this scope / mount combo but I am curious as to how it will perform. Will post the results...

Lovely image, as ever.

Love it. amazing with a DSLR...

I've had my CEM60-EC since 2014 and I've been delighted with it. In fact the first three images I captured using it were published in S@N magazine / Astronomy Now. I've recently updated the review on my website if anyone is interested as I believe pretty much all my minor quibbles have now been addressed. After some early firmware issues the encoder now works extremely well and I would thoroughly recommend this mount.

I've also done this sort of thing to an audience of non-experts. I tend to cover the broad principle of correcting for the Earth's rotation which leads nicely on to guiding (nothing too technical, just an explanation that you point at a star you're not imaging and movements of that star are used to correct for the movement of your target). Then I've done a bit on the principle of digital stacking - again in simple terms pretty much as Carole suggests. I have done a bit on narrowband imaging and I think have just about got away with explaining the physical principles behind emission nebulae with the help of a diagram or two and how that translates. I agree that people always seem interested in how far away things are, and of course that gives the chance to say that when the light hitting my camera left this object then dinosaurs were roaming the Earth (or whatever)... Have fun with it!

Really nice image Emil - I have a bit of a soft spot for the tadpoles... Yes it's definitely worth building up the separate filters in photoshop so that you can go back and tweak each channel. There are great online guides to show you how to do this step-by-step but in précis you load up a frame from whichever filter, add a hue / saturation adjustment layer above, select colorise (colours are 0 for red, 120 for green and 240 for blue), saturation to 100%, brightness (or whatever it is - doing this from memory!) to -50. Then add a curves adjustment layer above and finally a levels adjustment layer above that. Select the three adjustment layers (which should all be above the image), right click and select create clipping mask and finally set the blending mode for the frame to "screen". To get the Hubble palette colours you can follow Bob Franke's guide.

It sounds like your flats are over-correcting for some reason. I'm not familiar with APP but can you post one of your flats? Have you tried processing the image without flats?

I can see why the confusion arises here but I think it's terminology about adding and subtracting and negative numbers... So for my FSQ85 reducer I need a spacing of 72.2mm. If I have a 3mm astrodon filter in the image train it pushes the image cone outwards by 1mm so the spacing requirement is increased by 1mm to 73.2mm. You are ADDING to the back focus requirement. So to make that 73.2mm I have: Atik OAG: 24mm Atik EFW2: 21.8mm Atik 490: 13mm Spacer: 14.4mm =73.2mm - the impact of the astrodon filter has been taken into account by increasing the required back focus distance. Now alternatively you can include the impact of the filter on the imaging train calculation by including it as follows: Atik OAG: 24mm Atik EFW2: 21.8mm Astrodon filter: -1mm Atik 490: 13mm Spacer: 14.4mm =72.2mm In this instance you are SUBTRACTING the impact of the filters on the elements contributing to your backfocus. It might help the penny drop if you calculate the spacer required in both of the scenarios above. Spacer = 14.4mm = -73.2mm + 24mm + 21.8mm + 13mm = -72.2mm + 24mm + 21.8mm - 1mm + 13mm Is that clear?

Yep it's well worth it. I resisted for ages, trying everything to avoid dust on my optics and vignetting, but flats made a big difference to my images. I still try very hard to keep my stuff dust free so I just shoot a set of flats for each scope / reducer / camera combination and use those. The t-shirt method seems to work fine for me, but at some point I would like an EL panel... Good luck, and keep up the good work! Ian

That's a great 1st guided DSO - well done! You should be able to take some flats to address the vignetting later so long as you can get the set up the same and roughly the same focus (the precise positioning of the elements in the imaging train is only required if your flats are correcting dust bunnies etc.)