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# jif001

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• Rank
Vacuum

## Profile Information

• Location
Warrington, England
1. ## Is my polar scope fitted correctly?

Yes that’s it - your starting point needs to be correct if your end point is to be correct. the red cross won’t move when you rotate RA, but if it’s in the wrong position to start with then it will always be in the wrong position. in the example the dodgy reticle red cross is aligned to a position to the left of the pole, not the right - have another look Think of the reticle as a wheel you can roll along the ground. In the first image the 6 is in contact with the ground. If I roll the wheel to the left so that the Polaris yellow cross is in contact with the ground and the broken line is vertical - i.e. it’s moved to the position in the second image - then the central red cross will have moved to the left.
2. ## Is my polar scope fitted correctly?

See if this helps ... Here I have two reticle screen shots. One has zero exactly at the top, which is what I want, and the other has an error whereby zero is not exactly at the top, and I’ve grossly exaggerated this error to illustrate the point I’m about to make (I’m not good at judging when it’s exactly vertical but I’m better than this!). Ignore the blue lines for a minute Remember, what we want to achieve is polar alignment, which means the red cross in the reticle needs to coincide with something we cannot see - the celestial pole. Luckily there’s a nearby star that we can see, Polaris, and we use it as a guide. By getting Polaris in the right position in the reticle, at the correct angle, we know that the red cross hairs are aligned with the celestial pole. An app or other means will tell us the angle we need. Look at the broken line joining the position of Polaris (yellow cross) to the central red cross in each case. In the second image my exaggeration of the tilt has made this line deliberately vertical so it’s easier to illustrate the error it creates. The true position of the celestial pole is where the red cross is in the first image, but you can see that the rotation of the reticle in the second image has moved the red cross to the left of where it should be - imagine superimposing the second image on top of the first so that the two yellow crosses exactly coincide. What you would see is the red cross of the superimposed second image approximately where my blue lines cross each other in the first image. What this shows is that if my reticle is tilted when I polar align then my scope is NOT aligned with the pole. If I used the tilted reticle below to polar align then I would be aligning with the blue cross in the first image. The real error you might get by having your reticle not exactly vertical is much smaller than this, because it won’t be this far out, but it’s an error nevertheless and will affect your tracking. Remember also that you need to establish the correct (vertical) reticle position (as in the first image) once only, and then mark your mount so you don’t have to do it again - just align the marks on the mount and you know you have the equivalent of image 1 and no tilt as in Image 2.
3. ## Is my polar scope fitted correctly?

I can’t comment on the ‘bubble’ reticle with any authority because I have the clock-type (as above) but I’m sure the principles are the same ... if you look at the reticle screen shot above you’ll see a yellow cross. That’s where I need to put Polaris in my polar scope reticle in order to polar align. Get it there and I’m done. However, for my polar alignment to be accurate I need to know that when I do this the reticle zero marker is at the top - i.e. exactly at the top, dead centre, with the line between it and 6 exactly vertical and the line between 3 and 9 exactly horizontal. That’s something I cannot achieve by eye because my eye is simply not accurate enough. I may get zero to look like it’s at the top, but is it exactly at the top, I mean, EXACTLY? So I used the method I described - get Polaris (actually any star will do for this bit but Polaris is best placed) dead centre in the cross and then using ONLY the vertical adjustment of the mount move the star up to the circle. Having done that I know EXACTLY where the zero should be and I adjust the RA axis so that the zero in the reticle exactly coincides with the star position, then I lock it and mark the mount so that I can find this position again without using the polarscope. I can then be confident that my reticle is in the precise rotational position for aligning with Polaris when I need to polar align. All of this is aimed at finding the correct reticle position only. It’s a one-off procedure and the marks on the mount are now my reference points for getting the reticle in the correct position prior to polar alignment. The video you’ve seen elsewhere using the bubble reticle is just applying this principle - getting the reticle in a known rotational position so that polar aligning can be done accurately. You can polar align without doing this, but it won’t be as accurate. That doesn’t matter for observing where a bit of drift won’t spoil it, but if you are imaging then any drift at all is to be avoided. Let me know if it’s still not clear - I’m happy to try and explain it again if necessary because I would have been glad of some guidance like this myself and I get why it might be difficult to grasp! I’ve already suffered your frustration!
4. ## Filter Choice

Thanks for the response. There’s more to this than I thought. Having been enlightened by it I googled ‘chip size vs filter size’ and it led me right back here to this useful thread:
5. ## Filter Choice

Had a good old rummage around but haven’t found an answer to this so here goes... 40 years after life got in the way of astronomy, and after 35 years of employment, I’m now in the happy position of being able return to a great hobby and to kit myself out with proper stuff, my aim being ultimately mono imaging with filters. I have a scope (Altair Astro StarwaveAscent 102ED) and Mount (EQ5 Pro GOTO) and currently use it with a Nikon D7200. The next step is a mono camera and filters, but which filters to buy? This isn’t a question about Ha, Hb, Oiii, Sii, but about the merits of 1.25” vs 2” It seem logical that the larger aperture of a 2” filter would be better, but is that the case? Would an all-2” setup be significantly better than an all 1.25” setup? Does it warrant the extra cost?
6. ## RA/DEC clutch tightness? HEQ5

1) yes you can if you unlock then clutches, as stated. ‘Alignment’ can mean two things - polar alignment and GOTO alignment. The clutches don’t affect polar alignment so you will not lose polar alignment unless you also move or otherwise adjust the mount. However you will lose GOTO alignment. Your GOTO relies upon starting from a known position called ‘home’. In this position it knows where the scope is pointing at the start. If you then unlock the clutches and move the scope the GOTO doesn’t know anything about it. see my comment near the bottom of this thread regarding home position and how the GOTO works:

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