ollypenrice

Yes, I know, that's the one we have here. Terrifying!! Olly

No, Ha is remarkably moon-proof, the narrower the bandpass the better. There is a huge difference in partial moonlight between our 3nm Astrodon and 7nm Baader. Other NB filters are hardly effective at all. (OIII is no good in the moon.) For all that, even with Ha the moon needs to be well away from full phase so I agree with Sara. Olly

Hi Ian, Yes, I used the 4000 with the 200mm Canon. At the time I had OSC 4000 and mono 4000 so I tried Ha from the mono and 0SC (RGB) from the OSC. I did a wide M45 with just the OSC, too. The coarse sampling rate shows up in a loss of fine resolution and, more importantly, perhaps, in a blocky look so far as the stars go. If you keep the image presentation size small it is bearable but you can't offer the results at full size. In the end I regarded these results as interesting and as an inspiration to come back at a finer pixel scale and multi panel mosaic. I'm trying to link to a couple of images I did with this setup but the net won't play. Sorry about that. I image (as do a lot of people) at 3.5 arcsecs per pixel with the FSQ106/Kodak 11 meg combination. That is about as coarse as I ever want to go, I reckon. Olly

I don't know. It might be tight to get a F/W in there but I think someone (Gerd Neumann, maybe?) made a slide drawer for CCD to camera lens. This is only going to work sweetly for CCDs with very small pixels. I used a Geoptik CCD-Lens adapter and it can take filters, but involves a full disassembly to change filters. I know someone who's done this but it would be a step too far for me. Cameras with integrated filterwheels (QSI and some Atiks) might have a short enough backfocus requirement. In fact I think they do but this would need checking. Olly

Tak Baby Q, reduced, F3.9 and Tak 106, reduced, F3.6... ... but a whiff more pricey than a 200L!!! I've used the Canon 2.8. It was very good but my CCD pixels were too big for it. TS do a micro-focuser. Olly

Tom's right, a sticky of cause and effect distortions would be a great resource. To be honest, I couldn't contribute to it because I've imaged with a WO ZS66, TeleVue Genesis (late eighties, F5), Meade 127, Altair Astro 102 and 115 apos, Tak Baby Q, two Tak FSQ106Ns and a TEC140 without ever having encountered any distortion problems out of the box - including some very old boxes... (This ignores visiting 'guest scopes' such as two other Baby Qs and two other 106 Taks, another TEC140 and - quite honestly, I forget the rest. But it does add up to a lot of refractors which just worked.) I could be wrong about the effects of tilt but I use refractors because- sorry to be boring - they just work. Olly

This is not just disgraceful, it is plain potty. Why on earth should a refractor of around F5 not 'just work?' It is hardly an insanely fast astrograph and that is the whole point of buying an FSQ. It's a 'sanely fast' astrograph and should be simple to use. We really have heard some strange ideas from Gnomus' vendor on this thread. I have literally thousands of hours of DS imaging time logged on three Tak FSQ instruments. The first was my Baby Q, bought new, and now used to well known good effect by Sara (with the very 8300 chip which the retailer considered, bizzarely, to have too-small pixels. It is probably the most-used chip with the Baby Q, world-wide.) The other two scopes are second hand FSQ106Ns belonging to myself and Tom O' Donoghue, the rig which just produced runner up image in the Astrophotographer of the Year competition. To put the second-handedness of my own scope into context, it arrived after Parcel Force had bashed a hole through it's flight case. Not in the first flush of youth, then? No, not really. But does it 'just work?' Of course it does! So does Tom's. So did my Baby Q. So do the FSQs (two of them) working in my robotic shed on behalf of their owners. (No, one of them needed the focuser tightening, to be fair.) And so did the three visiting Baby Qs belonging to guests here and whose images I helped process (including ones taken with three micron pixels.) The FSQ isn't a Hyperstar or some other bit of optical madness built without regard to the harsh realities of engineering. It's supposed to work and most of them, in my experience, do work - even after Parcel Force have molested them. I smell snake oil. Olly

Hmmm... I'm not sure it's Takahashi engineers who've been looking at this so much as the Tak importer who is essentially a retailer. I've seen never seen tilt produce what looks like a spherical distortion and one limited almost entirely to the corners. The CCDI curvature test shows curvature on the extreme right hand side and at its worst in the two affected corners. Of course I could be quite wrong but I cannot see tilt behaving like this. Olly

Radial distortion cannot be tilt. Simple as that. Ian King's opinions need no endorsement from me but, FWIW, I do agree with him. You might well find tilt in CCDI on Steve's images but that tilt cannot be the cause of the problem. (You might find a crack in your car's windscreen but that won't be why it doesn't start.) Olly

And there you have them. Olly

Thanks, Steve, he did! I've been out of bed for the large part of four days and it's beginning to show... The Baby Q is a good match with far smaller pixels. Note Horwig's post here. http://stargazerslounge.com/topic/255014-deeper-into-m31-from-les-granges/ I worked on this data so I know it's genuine and the pixels are far smaller than those of the 8300. Olly

Good grief, you are resolving at 2.47 arcseconds per pixel which is positively coarse, so the claim that your pixels are too small is risible. The UK 'sweet spot' is often estimated as being at 2.0 arcsecs per pixel and you are well above that. Imaging down to 0.6 is commonplace. I did it for two years on a full format camera. Many of my friends ask why I put up with 1.8"P/P on the TEC140/ full fformat outfit and I say, 'because it's nice and tolerant and relaxing to do.' So your pixels are on the big side, not the small side, and you'd have plenty of imagers to confirm this. On top of that your chip diagonal measures 22.5mm for a claimed imaging circle of 44mm so you are using a tad over half the full circle. So you have a forgiving pixel size and are using a chip which exploits about half the light cone. Reality check, you should not even be taxing the optics in the slightest. Sara can prove that a Baby Q can cover this chip easily. However, the tilt remains a possibility. The fact that it wasn't there on the ED80 may not be proof of the chip's orthogonality because the Baby Q has a faster F ratio and so greater depth of field. And I do suspect that, while it may not be perfect, you might have a very hard time beating the Baby Q once you get into long colour exposures... As for that stuff about pixel scale, it's bunkum. Olly

I did so and thought it perfect. However the corrected circle on the 106 is so big that you can't find a camera to test its potential. A good thing for all our wallets, I dare say... I'm glad you'g getting a new one to try, Gnomus. Olly

Yup, that excludes PA conclusively. I'm really sorry you're having this hassle. Olly PS I'd send that crop to the supplier.

You shouldn't have to focus on the one third lines with this scope. Having been absolutely delighted by mine (which is now Sara's) I have often extolled its virtures but both Steves have had issues and this is not good. It's a great shame. My subsequent Tak experiences (using my own very second hand FSQ106N and Tom's similar instrument) have also been entirely positive (not that this proves anything. I just mention it.) At the resolution available on here I find it hard to tell whether or not the corners are worse in the 5 min subs. What do you think, Gnomus? Olly PS I had my first Mesu nightmare last night but it turned out to be my fault. I had somehow managed to reverse the sign in the encoder steps setup menu. (Or it might have been the cat. I bet she did it!) The Mesu continues to 'just work' in a way that seems to be beyond the powers of much of the kit we use, as Steve Steppenwolf says. And, further to Sara's point, this thread would be a good port of call for anyone reading here. http://stargazerslounge.com/topic/256544-a-couple-of-star71-wips-m45-m31/

I wouldn't try to collimate it! It was the focus adjustment that I think you might be able to tweak painlessly if you find evidence of sag. If it's out of collimation in needs to go back. Olly

Good ideas from Mark and Sara. A meridian flip on a southern target would turn the scope over but the target would be the same, so you'd see if the distortions reversed themselves as they ought to do if it were the focuser. (I'd give it ten minutes to re-sag, so to speak...) This is certainly becoming a candidate. If the sensor were not tilted in its previous scope then why would it be tilted in this one? If this doesn't happen then we'd be looking at slight mis-collimation which is not unknown. I know that Per has discussed the Tak focuser and one place to ask for advice on adjusting is Texas Nautical Repair, who are very expert on all things Tak. Olly

Indeed so. The Mesu is a good mount! Olly

I would say that the present distortions are, as you suggest, the result of field rotation. And yes, I would expect this to be worse on a wider FOV. The simple test is to take a short exposure through a less restrictive filter (luminance) to see if the distortions are still there. In a short sub rotation won't show. On occasion my PA needs a tweak and a rotation visible in 30 minutes may not be visible in 15 minutes. Looks like you're on the road to success! Olly BTW, below is a typical Mesu guide trace in AstroArt 5, my eccentric choice of guiding software. The guidescope is the same as yours, so has a 400mm FL and the Lodestar is working in bin 2 so a hefty 8.46 arcsecs per (virtual) pixel. The graph is in pixels. I run 4 second guide subs. I can refine this level of accuracy by working on it on a night by night basis but at the scales at which I'm currently imaging on the mount it would be a waste of useful time to do so.

Cheers, Steve, so now I'm wondering whether that argues against flexure on the grounds that most of the correcting applies to RA. On the other hand a flex in Dec would throw up a spurious command. Perhaps it doesn't tell us anything. I might be thinking about tilt again, though. Olly

Do we know the RA-Dec orientation of the elongation? Olly

Yes. I used a Baader saddle bolted onto the clamshell. Then both my solarscope and guidescope, on Vixen rails, could be swapped easily for each other. The system also allows easy fine tuning of Dec balance by sliding the guidescope fore and aft. Olly

Thanks Hawksmoor, that's very kind of you. We're glad you enjoyed it. We certainly did! Olly

I honestly don't remember a tilt adjuster module on mine. I'm not at all sure that I had one, but Tak do change things around with their hardware. I certainly never used it since I didn't know about it. Well, it looks as if nobody likes that guidescope carrier and, on single scope setups, I've never had any issues arise from approximate alignment of guidescope and imaging scope. While I like and use (two) ST80s for guiding there are a couple of things to watch, though I doubt you've missed them. The entire rear end of the scope is held into the main tube by three screws. These need to be very tight. I wouldn't baulk at a drop of epoxy to hold the back end in firmly, either. I did have the back end cause flexure once. The drawtube is also very vague so I tighten the lockscrew rather pitilessly to keep it still. Any extensions carrying the guide camera also need careful attention. Olly

OK so bin my suggestion about PA if the guide scope is on axis. I have to say that I never like adjustable guide scope holders or rings* and always prefer a bolted-down guide scope even if it isn't perfectly on-axis. With good PA this won't matter. That adjuster has to be a suspect, though it may be perfectly innocent. I guess the orthogonality of your filters could play a role but does changing filter change the distortion? If not it's highly unlikely to be that. (You'd have done well to replicate the same tilt in every filter...) Olly *Except in the case of dual rigs where, on two occasions, we've found the system prefers an on-axis guide star. I can't account for this. It could be experimental error but it happend twice so I just accepted the fact. PS, I found the Tak and reducer to be a stunning combination and Sara always runs the reducer, I believe, so I wouldn't be put off it too easily.