Robculm

No, didn't use a filter for either. I do have a UHC (Explore Scientific) which I've previously been using on nebula targets. Will certainly be experimenting with that on the modded camera at some point. Hopefully there's now enough Ha transmission to warrant it reduntant. Problem I found is that although it certainly helped exagerate the Ha (pre-mod) you lose the natural star colour, rendering them all either blue or red as you're essentially blocking everything in between!

Here's a link to the description of this on Andy's page: http://astronomiser.co.uk/filters.htm So mine was the 'rear filter removal with sensor repositioning'.

Ha, yes, the terminology is somewhat confusing. I didn't have the full spectrum mod, so I guess you could call it the Ha mod, yes. Now I just need to resolve my star shape problem (which looks like a collimation issue after some more fumbling around with alan keys in the dark last night!)...

Ha, yes, tell me about it! But I guess if it was too easy it wouldn't be so rewarding / addictive! Sorry, will need to defer to others on the camera question. I have the https://www.firstlightoptics.com/zwo-cameras/zwo-mini-finder-guider-asi120mm-bundle.html which to be honest I randomly selected, but it seems to work OK for me & it's light (200PDS is already a heavy scope for the HEQ5 without too much additional clutter!). I believe there are mathematically optimal guide camera / scope criteria to match with specific telescope / camera configuration... Nothing is as straight forward as it first appears in this business!

Just to add, I realise of course that this is perhaps not the best target for showing off an IR filter mod! I'm looking forward to using it on something like the horsehead nebula in due course... But that said, making something red even redder is perhaps not as exciting as showing the colour where it's just not visible pre-mod! I excitedly showed the 2 images to my daughter this morning & she said she prefers the 'blue' image! 🤣

Hi All, Keeping in mind these are both minimal data (~1h of 5 min subs), no calibration frames, 5 min processing in Startools & yes, I still have some star shape issues to resolve 🙄. But I was so excited with the result I wanted to share! 😁 M33 obviously. Before & after the camera mod (by Andy Ellis http://www.astronomiser.co.uk/). Received it back yesterday & despite the questionable forecast, managed an hour of reasonably clear sky...

Hi Danny, I see you've got lots of good feedback on this topic already, but I just wanted to add a quick comment since those elongated stars are oh so familiar to me!!! I have the 200PDS on an HEQ5 mount & spent hours & hours optomising this & that, fitting the rowan belt kit etc etc... About 3 min was the max exposure length I could work with & even then I'd usually be throwing away 50% of the images (which is really really frustrating). Autoguiding solved the problem. So just to highlight that you will almost certainly need to go down the autoguiding route, even if you upgrade the mount. It might be worth experimenting with autoguiding on your current set up to begin with, rather than spending out on a new mount & finding that while it may improve, it will not necessarily resolve the problem! Good luck, Rob

Mirror clips removed, glued in place with RTV silicone (after replacing the screws with M5x35mm) & blackened around the chamfered edge. Hopefully it's stuck down well! 🤞 New springs (1.6mm wire, 20mm length), washers & lock screws to push the mirror forward so that the focus tube 'inclusion' is reduced... Also discovered that it's much easier to see if the spider vanes are 'straight' while the primary is removed (i.e. looking up from the 'bottom' of the tube), which they weren't on a couple... and made some adjustment to the secondary centration... As I mentioned, camera is off with Andy Ellis for modification now, so unfortunately can't test for the moment. Will post results when it's back & there's a clear night...

👍 perfect. Thanks again 😀

Thanks barbulo & thanks Vlaiv for the detailed response 👍. Now I just need to figure out how the Startools binning scale corresponds to this! It's not clearly defined (at least to my interpretation), but I guess 50% is equal to x2 binning? Cheers, Rob

Hi, can anyone please confirm I'm understanding this correctly & your recomendation! With my 200PDS + coma corrector / reducer, I have a focal length of 900mm. EOS800D has 3.7um pixel size. Gives a resolution of 0.85" per pixel according to Astronomy Tools. The ideal pixel size for Good Seeing (1-2" FWHM) seeing is: 0.33 - 1" / pixel & for OK Seeing (2-4" FWHM) seeing is: 0.67 - 2" / pixel. So with good seeing, probably even OK seeing, I'm in a good spot in terms of optimum 'sampling', which implies that I shouldn't bin? Since starting with Startools, I'm generally binning (software) by 50%, mainly to reduce the 'size' & help with processing speed (I have a reasonably new laptop, but it's fairly basic & certainly struggles). Should I be exploring a faster computer (or just be more patient) & keeping full resolution, or binning by 50%? Don't want to risk losing good data when it's so hard to come by! Cheers, Rob

Yes, that's a wise suggestion. I did find this UK company with a good range: https://www.leespring.co.uk/compression-springs But I have to admit I got a bit lost browsing the 16,000 options! Will take another look...

Ha, yes, working on that that one. Have the longer screws (+ washers for the springs rather than replacing them). Will put these in when I silicone the mirror... 🙂

Haven't embarked on the silicone exercise yet. But I loosened off the mirror 'clips' & repeated the same image. Definitely an improvement 😀. Actually my 800D is booked in with Andy Ellis for modification in a couple of weeks, so will have a go at removing the clips completely while it's away & see if it improves things further... Note, same ISO / exposure, just earlier in the evening, hence the brighter background on the 2nd image!

I couldn't guarantee it's a good choice, at least until I've tried it! But the one I've ordered is: https://www.amazon.co.uk/gp/product/B01C4RYE76/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Thanks Steve, Thanks Alacant. Considering the thickness, it's hard to imagine huh! But fingers crossed this is the cause. Looking back at my previous images, it does appear to have changed over time, which could tie up with me having taken out & cleaned the mirror on a few occasions (I'm a bit festidious about the mirror cleanliness, despite some peoples suggestion it's not important!) & my recent update putting the longer screws in to push the mirror forwards... Anyway, it's an easy one to try, so will report back as soon as we get another clear night! I love the silicone RTV approach Alacant 👍. Have just ordered a tube from Amazon. Will make cleaning the mirror much easier too! 😁

Hi all, Just playing with optimisation at the moment in the brief clear moments... Here's an M31 image from earlier this evening (yes, it's a little too large for my FOV!), no calibration frames, just 30 mins of data, 3min subs. But more importantly, it quite clearly shows the star shape problem I'm having! Any suggestions? I'm pretty sure the focus is near optimal & have spent a lot of time on collimation. But can't seem to resolve. Guiding is 'reasonable', around 0.6" total, fairly equal in both RA / DEC. Many thanks, Rob

Fantastic result & a great use of a clear moonlight night! Here's me wasting the night just optimising guide settings & wondering why there always seem to be more clear nights when the moon is up?!?! Can I ask if you bought your 800D modded or where you had it done? I'm contemplating the same for mine, just a little worried about comments I've seen regarding 'star bloating' on modded cameras... But would love to get a little more Ha...

So first 'proper' session with guiding & my new Asi AirPro set up. ~5h (300s lights with OHC filter) Stacked in Siril & processed in Startools (huge thanks to Alacant for his advice and incredible patience!). Ha, isn't it great to have a passion where you actually look forward to the long dark nights of winter!!! Rob

Well indeed! Good news is that despite appearances it worked a treat & I managed to get >4h of data 😁. Scary moment after I changed the camera battery & did a quick re-focus mid way through. Had overlooked that the target was across the meridian & the dew shield crashed in to the fence while travelling back to it! Anyway, together with the hour or so from Friday night, total ~5h of data (300s exposures), here's the preliminary result. Haven't added calibration frames yet & it's just a very basic edit (I think maybe I was a little heavy handed on the colour saturation slider though!).

Ha, so far so good, but we're only 10 shots in ... Not sure it's doing much for my guiding, even on such a still night! I guess there are particular times of year where the dew is more troublesome? I didn't have a set up that leant itself to long sessions until now, but can't say I noticed any problems with dew in the winter, even when the outside of the tube, well pretty much everything, was soaking wet at the end of a session. Is it particular to this time of year when it's a little warmer but cooling in the night?

So I've discovered what this dew business is all about! 😭 What should have been a good 4 - 5h of data ended up as around 1h before mysterious halos appear, expanding in to well, nothing much at all. Looks clear again tonight, no time to order in a professional one, not even time to order a black camping mat on Amazon, so here's what I've cobbled together this evening! It's lined with black paper, so hopefully will work somewhat better than it looks!

Despite many attempts at collimation, I still don't think I'm quite there. I've used a combination of Cheshire & laser pointer. Blocked out the primary to get the secondary centred in the focus tube etc & all looks good, except I;m really not convinced I;m getting the rotation of the secondary correct. It's very difficult to see when it's exactly circular. I downloaded ALS Collimation aid, which provides a circle on your computer screen, but of course I need to view down the focus tube with a camera. Ha, yes, of course that's what we always do when we're imaging! But unless I'm doing something stupid (or unless perhaps I just am stupid 🤔), that won't give me an image of the secondary. I also tried the guide camera, but didn't seem to work either, again because neither has a lens, just sensor I assume). So, am I correct in thinking I need some kind of webcam, with built in lens? If so, can anyone recomend something really cheap, as I only want to use it for this purpose! Cheers, Rob

Ha, nightmare. I'm always a little nervous about making any significant changes to the secondary for fear of making things worse. Actually I did brave a major re-alignment though & I do appear to have somewhat reduced the difference in focus between the two orientations. Secondary centration in the vanes was out a little and I think the centration in the focus tube slightly off, also spent a lot of fiddling time to get the circularity as good as possible. While I was at it I brought the primary mirror forward as far as possible (with the stock fittings) which drops the draw tube out by a couple of mm's. There is a lower profile focus tube adaptor available https://www.firstlightoptics.com/adapters/astro-essentials-2-inch-compression-ring-adapter-for-sky-watcher-newtonians-and-72ed-refractor-m54.html but it only gains ~1.5mm (and out of stock), so as per Alacant's suggestion I will probably look at custom springs / screws for the primary to push it forward more significantly. Should add here that I also discussed the topic with Alex at FLO. As always, their level of knowledge & advice really is outstanding 👍. Anyway, I'm keeping the set up as is for now until I get chance to try it out for a decent imaging session. My plan was to try & catch NGC6960 in this next moon free phase, while the nights are getting longer & it's still just about reasonably positioned... However...

Thanks for the replies / suggestions. Rotating the camera is an easy one! Will give that a try this weekend. Will also 'poke around' and try to figure out where the other 'feature' that's not the draw tube is coming from. Also plan to check again the collimation in terms of secondary positioning (centering), checking it's central in the vanes & I thought to check how central the primary is & check the centre spot really is in the centre! Alacant, regarding your comment, I have definitely noticed the draw tube exteds quite some way in to the tube, becuse at prime focus it's almost fully 'in'. When you say extend the screws / springs to move the mirror forward, you mean in order to push this out, so prime focus is a little further out? I had comtemplated taking a hacksaw to the draw tube, but thought that might come back to bite me if I ever change camera / set set up which requires it to be extended further out!!! Ta, Rob