ollypenrice

I owe Ian King an enormous debt in terms of the sound advice he offered me when I decided to embark on DS imaging, advice I often pass on to this day with its source acknowledged. It can only be a good thing that two completely reliable and expert astronomy retailers are merging like this because your overlapping specialities and areas of expertise seem to mesh so well. I can only wish you well for the future and do so with both my head and my heart. Olly

At my best in cycling I would've been fourth best junior girl in Britain over ten miles! I just wish your observatory would take on even the tiniest hint of scruffiness. As it is I daren't go up to mine for shame until it's dark and I can't see the inside! Olly

I remember Sara saying this as well but it has never affected my PA efforts. There must be a reason. How about this: in the threaded system which pulls or pushes the mount east or west there must be some backlash because there always is. Now the top nut turns clockwise so if the adjusting system has its backlash still present for a clockwise movement of the mount you'll get the effect you describe. But if that backlash has already been taken up you won't. What I'm thinking is that whether or not a final turn on the centre nut will move the mount will depend on the direction of the last thing you did with the adjusters. It might be worth checking that the adjuster's backlash is on the 'anticlockwise side' and is already taken up. Does this make sense? Olly

Possibly so, yes. The trick, I think, with any kind of mechanical adjuster that has to be locked finally in place is not to have it too free to begin with. I keep a fair bit of tension in the moving (adjustable) parts before final tightening. This applies to anything - engine tappets, motorbike rear wheels for chain adjustment, etc etc. Olly

We seem to come to the same conclusion here. I very much doubt that real results would change by much. If you have a site with exceptionally stable seeing the 16 inch RC would indeed deliver a new world of wonders. In most parts of the world, however, it would deliver a shedload of 'empty resolution' onto a minute FOV! I didn't want to sidetrack the mount thread but merely raise the issue of the value of this increased payload because that might impact on mount choice. Olly

I'm trying to think of what you mean by the mount rotating during PA. I'm observatory based so it's a long time since I did a PA but I honestly can't remember any issue like this. I do remember installing the first one here with its original owner and we both thought it was incredibly easy. We aligned using drift. I did use the polarscope when I installed our second one and, again, I remember it as painless. One guest brings his Mesu most years and sets up very quickly, too. I'm not saying you're wrong, just that I can't imagine the issue. The housings round the drive wheels are fabricated on all but the first Mesus and are more angular, I agree. On ours they are rounded and one piece. (How they are constructed is a bit of a mystery, rather like a ship in a bottle!) Olly

It won't be faster if the imager has to do a mosaic to replace the reduced FOV. If we allow ourselves complete freedom to invent any camera we like then the 16 inch will beat the 12 inch because we can invent a camera with a larger chip to replace the lost FOV of the 16 inch (though we might need to invent a new coma corrector as well). We can also invent a camera for the 16 inch which has not only a larger chip to restore the FOV of the 12 inch but also has larger pixels to hit the sweet spot of 0.9"PP (or whatever). The problem is, once we have invented these cameras do we know anyone twitching with enthusiasm to make them for us? And since the future seems to be moving away from CCD and towards CMOS the simple binning solution (which I have never believed was that simple anyway since not all cameras bin well) becomes not so simple. Olly

Larger scope means more aperture? Damn, I hadn't thought of that!!! Seriously, I think everything I have to say is included in my first post which is strictly devoted to comparing 12 inch F4 and 16 inch F4. Where, in your view, does the 16 inch win in seeing which is limited to, say, an arcsec per pixel? (I always enjoy our disagreements!) Olly

Isn't that exactly what I said??? lly

That's not what I'm saying. Note that I'm comparing a 12 inch F4 with a 16 inch F4, not a 16 inch with the same FL as the 12 inch. The question is not whether a small scope and a large of the same focal length will be equivalent. They won't, as you say. The question is, what will the OP gain by moving from a 12 inch F4 to a 16 inch F4 bearing in mind the FL will increase? In my opinion both will be seeing-limited and risk resolving detail at the same level but with a loss of FOV in the large one. Olly

What do you expect to gain from the 16 inch for deep sky imaging? The 12 inch has a FL of 1.2 metres. The 16 has a FL of 1.6 metres. A FL of 1.2 metres with modern cameras will easily take you to an image scale of below, or even well below, an arcsecond per pixel. What resolution will your sky support? If it will support scales below an arcsecond, at least on any kind of regular basis, I'd be amazed and would be similarly amazed if the theoretical gain in optical resolution would translate into new details resolved on the image. We are seeing-limited. I'm struggling to find much improvement in resolution when comparing data from a 5.5 inch refractor at 0.9"PP with data from a 14 inch reflector working at 0.6"PP. (Different cameras.) I ask this because the big scope is part of your mount game plan. Personally I'd go for the bigger aperture for visual but not for imaging. I can't see the point. I think you'll end up with the same final resolution and a smaller FOV. In any event, even the 12 inch can take you into imaging territory where you'll want a guide RMS of 0.4" and that's a high level of precision. For me the EQ8 is a big hefty mount more than it is a high precision one and for that reason I'd go for the iOptron. (That is if I couldn't find a second hand Mesu. Both mine cost less than the new price of the iOptron.) Olly

Are Mesu mounts attractive? You bet they are. Olly

Copperslip! As has been said, tilting the mount slightly is the obvious answer. While a mount which isn't level E-W may need more iterations of the drift method since the two axes will interact slightly, being tilted N-S has no effect whatever on anything (provided the thing doesn't fall over!) How does the polar axis know it's been tilted by the pier-tripod or by the pivot? It doesn't. They are equivalent. (The Avalon has a linear bubble level on the E-W axis only.) Olly

I'm not! Artemis Capture is perfect for me but I'm sure that, between them, the software brigade will oblige me, in the end, to switch to something they tell me is better. Olly

Provided your dovetail bar were a light one I would expect a camera and 200mm lens to manage with no more counterweight than the bar itself, though you could tape a metal bar along it for a little more weight if necessary. We've run cameras without counterweights on our EQ sixes here several times here without issue. Olly

Firstly your FITS headers should show which filter was used for which capture so you can, albeit laboriously, go through them all and put them in the right place. (I would make a separate folder for each filter and asign each checked image to the right folder rather than rename the files. That's just me.) I haven't used Dusk and don't want to because there is nothing wrong with Artemis so far as I'm concerned. However, could this have anything to do with the nature of the sequence you've chosen? Normally with sequencers you can scroll 1,2,3,4 etc or choose 1,1,1,1, 2,2,2,2, etc. Olly

My first scope, a TAL Newtonian reflector, did come with a solar projection kit (including little clips to hold a card so you could copy the sunspot positions onto it.) I didn't use it a great deal but never had a problem. However, I'd err on the side of caution regarding heat build up at the primary. Olly

That's cos all astro kit is now bright red! Olly

Exciting. Just a thought on the American plug, but US voltage is 120. Doesn't this cause a problem? Olly

Another neat idea is to make your own pinhole solar finder. There are some ideas further down this thread. Peter Drew's is a good method. Some people make their solar finders adjustable in angle to align with the viewing scope but the easiest way is to align it roughly, get the scope pointing at the sun, and then just mark the sun's central position on the finder screen you've made. Olly

The Baader film might actually be safer because it is a double sided filter. Once it's delivered it should be fitted into a permananent ring the size of the scope's aperture so that it undergoes no further crumpling and it should be cared for properly, stored in a box etc. When fitted to the scope it should have permanent ties holding it in place against wind or knocks. It can be easily checked for pinholes and these can be blacked out. They won't show for the same reasons that a secondary mirror doesn't show. Remember to block finderscopes, Telrads, etc., or you can get a nasty burn at the focal point! If you really are worried you could try the projection method. Google solar projection and you'll find many ways of doing it. Olly

Argh, the suspense! I look forward to your comparison since I know the Lunt 60 quite well. Olly

From the review: We achieved this using a 1600 ASI camera; changing to an imaging camera with a smaller sensor meant that the telescope was able to get quite close-up images too Whoops. Will this instrument show proms or is it strictly for the disk? It does look very tasty and I'm following with interest. Olly

Focus can drift on any telescope so reliable autofocus saves effort once you've got it working. Personally I focus manually but I'm old fashioned. However, I don't believe non-parfocality in mono systems comes from the filters but from the optics, so a mono allows you to refocus per colour if you wish while an OSC does not. As has been suggested already, in mono imaging the filter needing perfect focus is luminance (and any NB you shoot.) OSC is slower than mono because it cannot shoot luminance, which is catching R, G and B simultaneously so is extremely fast, and objects which are strong in Ha build efficiently in a mono rig. Like Carole I found OSC data to be rather difficult to process to any kind of good standard. Certainly harder than LRGB. Making an RGB in AstroArt goes like this: 1) Stack the R,G and B separately and have them open. 2) Use auto-align to align them in one click. 3) Use Trichromy, click auto white balance and auto colour balance and say Go. If this takes a minute I'd be surprised. Olly

I do absolutely need the one marked, Hello darkness my old friend. Where do I look???? lly