ollypenrice

GoTo works perfectly if the mount isn't level. Witness Takahashi mounts which cannot be levelled. My Tak Go To is first class. You can have a Tak mount polar aligned before a regular mount user has got the tripod level. That is literally true. My point wasn't about the speed of levelling, though, and Steve's right that it is better to level a mobile (non Tak) mount because of the interaction between azimuth and altitude drift iterations. My intention was to comment on a fixed observatory pier, the OP's topic, in which many designs compromise rigidity in order to offer levelling which is simply not needed. In a pier you want rigity. The real pests are the manufacturers who design mounts to be secured onto tripods or piers from below. For piers this pointlessly introduces the need for some form of access, so we get into ratboxes and owls nests and all sorts of silliness. Nowadays most manufacturers have woken up to this. Avalon, Mesu, iOptron, 10 Micron and many others now have systems which require no central access from below. Hooray!! Olly

Dec isn't level. If Dec is level you'll be looking at the horizon! Olly

This is a vexed question and is flirting with the dreaded F ratio myth. But firstly the only form of binning possible here is software binning because we cannot bin a one shot colour camera. Whether or not focal reducers 'speed up' capture depends on what part of the image interests you because what they clearly don't do is bring in any new photons from an object which fits on the chip without reducer. Viz; In my opinion you might just as well crop and software bin in the scenario above as use a focal reducer. If you downsize the native FL image the information it contains is concentrated onto fewer screen pixels and the image will look less noisy. This is why, when you stretch an image, you must always keep checking it at 1 to 1 because when software binned (downsized to fit the screen) the noise won't show. If you decide to present an image at 50% of full size you need far less data than if you want it to hold up at full size. I see no advantage here in using a focal reducer. Where a focal reducer really does bring in useful new photons is where it brings into the frame something you want to see; In this scenario you have useful light from NGC1977. The light from the empty sky around M33 was not useful. Of course the pixels 'fill' faster with a FR and the widefield M42/NGC1977 will reach an acceptable S/N ratio faster than the M42-only image on the left. But if you gave both images the same exposure time and then cropped out M42 from the right hand image it would be no better than the M42-only from the left reduced to the same screen size. Such is may take on all this, anyway. Olly

I know it can be odd at first but this isn't really hard to grasp. What does Polar aligned mean? It means that the mount's RA axis is parallel with the earth's axis of rotation. So if, in imagination, you took out your polarscope once the mount was aligned and fitted a steel shaft through the middle of it, fixed at each end to your observatory, it would then be impossible for your polar alignment to be imperfect. (It would get in the way of the scope but we're just thinking aloud here.) So now your mount has a steel shaft through its RA axis and cannot be moved by any means from perfect alignment. Now unbolt the pier from the floor and loosen the polar alignment bolts. In fact throw them away!! You can now tilt the pier forwards, backwards and sideways and the PA remains perfect. So there is no relationship between the angle of the pier and the PA. The main reason for levelling is simply to set the 'clock' in the polarscope reticle to vertical. (On Taks, with their potentially tilted tripods, you do this by means of a bubble level on the RA housing.) The other reason is that, in doing drift alignments, there is less interaction between drift tests in the south and then in the east or west. Maybe this is what Alignmaster didn't like when the mount wasn't level. My real point is that in an observatory mount there is no need to compromise a pier's rigidity by making it highly adjustable. Better rigid than adjustable if you can't have both. Olly

It would have to be quite a steep hill, in reality. This is actually metioned in the manual. And if Tak users live too far north for the rather limited adjustment in altitude they routinely put something under a foot to tip the tripod. By the way, I don't see how Alignmaster could have any knowledge at all of how the altitude angle was acheived (whether by tilting the pier/tripod or using the adjusters. The result is identical. Rather intelligently the levelling bubble on Avalons only runs east west, it isn't a circular bubble level.) Olly

Because round stars don't indicate good guiding. Random errors will produce round stars - but large round stars. I don't use Alignmaster and don't know how it works, but there is absolutely no doubt that mounts do not, in principle, need to be level. Try this thought experiment: take a perfectly aligned mount and get Harry Potter to hold it permanently in place by magic. In this situation you can remove the pier or tripod completely and Harry's magic will keep it perfect. Or you could shorten the tripod legs so they no longer touched the ground and then you could use the levelling adjusters to point the pier or tripod wherever you liked. The point is that this will have no effect at all on the polar alignment. The best fast PA routine bar none is Takahashi's and their tripods have fixed legs. Olly

If I have the right video in mind another member described it as 'snake oil,' which struck me as being about right. People go to a lot of trouble to make their pier tops adjustable so as to be levelled. In fact a mount can be perfectly polar aligned when the mount is not fitted to a levelled pier top. As I've often pointed out, up- market Takahashi mounts have no facility for levelling - because it isn't necessary. My own take on the 'snake oil' video was that the ground fastenings of the wonder pier being purveyed were too close to the pier itself. I always make piers with a reasonably large footprint. Olly

Not mine. It belongs to a regular guest. But mine certainly intimidate me in their own way... Olly

People using Newts for AP don't usually have the camera sticking out of the side. They rotate the tube so the camera is underneath, or pointing at the counterweight bar, if you like. If it's sticking out sideways you'll have trouble with dynamic balance - ie balance changing position during the mount's movement. Here's a very serious bit of imaging Newtonian in action at my place, Pieter Van de Velde's home made instrument. Note the position of the camera. https://pietervandevelde.smugmug.com/Pics/Equipm/i-gStw3gg/A Olly

Some impressive results and a good idea for a thread. Erm, would it be considered unsporting of me to go and beg some time on this Alt-Az instrument up the road from me? 0.8M Ritchey Chrétien, direct drive, field de-rotator and a price tag of 6 million Euros... Well it isn't an EQ!!! (There's always one...) lly

There is simply no way of knowing for sure which reducer will work with which scope unless a) it's dedicated to that scope by the manufacturer or, b ) it's been tried and tested by someone else. You could be confident that the dedicated SW one would work but it would be great to drop the F ratio still further with the AP. Provided someone can confirm from experience that the pairing works then that 0.67 would be a superb choice. If you decide to ask around do be sure to note the chip sizes that have been tried with the pairing. Very small chips are not an exacting test. A very common enemy of the focal reducer is the internal reflection on or around bright stars. Olly

That bottom flange has a suitably nautical look to it and is the right colour! Are you absolutely sure you haven't buried a Russian submarine in your garden with a bit sticking up for your scope? Olly

I use Baaders but have processed a couple of images with the Astrodon LRGB. I'm a fan of the AD narrowband but was slightly relieved to find myself vaguely preferring the Baader RGB set. This might be through familiarity but at least I didn't feel my Baaders had to go straight in the bin!! I like the Baader LRGB set. Olly

It isn't a case of 'better or worse' between the 3 and 5 Astrodons. The 5 passes the NII line while the 3nm doesn't. I use NB to enhance broadband images so I went for the very high contrast offered by the 3. It's discussed here. http://stargazerslounge.com/topic/206268-astrodon-3nm-versus-5nm-ha-filter/ To be honest I'd have thought that the Astrodons would be a big investment to use on only a quarter of the pixels with a DSLR. Olly

Well, the big Orion with Tom, of course. 400 hours, 33 panels, two focal lengths, etc etc!! Runner-up in the APOTY competition and more Tom's than mine. Still, I'll bung it in before he does! An HaRGB mosaic following structures in the North America region a bit forther south to see what was happening. Another mosaic from the Crescent down to the Tulip done with guest Paul Kummer. HaLRGB. Supernova remnant not so often seen near VdB152. (Lots of Ha!) And finally another mosaic uniting M35, NGC2158, The Jellyfish, Sh2 247 and the Monkey Head. Multi focal length, HaOIIIRGB. About 60 hours. An enjoyable year, as ever, and the Mesu has still never dropped a single sub. Cheers, Lucas. Olly

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