Pixies

Sky's The Limit (the chap who sells BST Starguiders) also sells the cheap laser collimator with the 3 screws under black silicone. https://www.ebay.co.uk/itm/Skys-the-Limit-Next-Generation-5mw-Laser-Collimator-1-25-2-adapter-7-levels/164350914583?hash=item264413f017:g:N60AAOSw2glfQ8TJ I ordered one and it arrived perfectly collimated, but that was probably luck more than anything else. I did build a collimation jig for the laser, though. I rarely use it since getting a decent Cheshire.

Hi, Here's my first ever moon photo, using prime focus: Bresser 8" dob, Nikon D3200. ISO100, 1/500th sec RAW NEF file edited in GIMP, for histogram stretch and slight sharpening. Saved as PNG Critical comments please...

I was just looking out the back door and saw an odd sight. 2 bright stars low in the north west. Realizing the brightest one was Vega, I could see the other moving. It was as bright as the ISS can be (obviously in the wrong direction). It rose close past Vega, fading all the time, and kept on going until it disappeared around 35 - 40deg alt. As I had nothing better to do, I made a note of the time (21:22) and then used SatFlare to work out what satellite it was - SL-6 R/B(2). So I confirmed it on Stellarium - and it matched exactly the path I saw. However, it says that this satellite was eclipsed at the time, and indeed - it's not a time or direction that I'd normally expect to see something, which was why I was interested in the first place. Could it have been reflecting light from the nearly full moon?

Cool. You won't need to do the secondary again unless it takes a big whack - or when you replace the adjusters with thumbscrews. Even then, it'll just be the final alignment with the doughnut. When you get a chance to observe with it, see if you can do a star test to confirm it's all OK. Normally, you should check the collimation every now and again. I do it each time I set it up, while the scope is cooling. All you do is put in the Cheshire and point a red light torch in the 45deg window of the Cheshire - then you can check the 'dot' is in the doughnut when you look down it. Most times, it's fine and doesn't need adjusting.

That looks great. Now remove the paper and fine-tune the tilt of the secondary, so that the doughnut marker on the primary is directly under the cross-hairs. Then that will be the secondary adjustment finished. Don't overtighten the adjusters, mind.

Both use the same data. I do find the website easier to use, though. If it's Android you're using, I find Nightshift quite useful too. When Nightshift and Clear Outside agree, it's usually reliable. But I wouldn't rely on any forecasts more than a few days ahead.

You mean this Tuesday: It's always clouds or full moon!

Thumbscrews like Bob's Knobs make it much easier to adjust the secondary while you are looking down the cheshire. They help avoid over-tightening too. You don't need to get something expensive like Bob's Knobs. Suitable thumbscrews are available as long as you know what size you need. If you are going to bring the secondary right back up the tube, take the opportunity to remove one of the adjusters and measure it. I think it might be an M4 bolt. You will need to work out the appropriate length, as they will need to be longer than the existing ones. I have a bagful of M4 x 40mm if you find this would be a suitable size - but they might stick out a bit (although that's not too bad a thing). Like these: https://www.amazon.co.uk/Thread-Knurled-Button-Thumb-Screw/dp/B0848PGF57 Alternatively, you can find plastic bolt head covers that will snap on to the head of a suitable bolt and turn it into a thumbscrew.

If you have trouble getting it level, one thing you can do is: Wind all the adjusters out and tighten the central screw until the secondary mirror is brought right up to the end of the tube as far as it can go and is flush with the end assembly. now you know it is parallel! Now, bit by bit, loosen the central screw and take up the slack by tightening all 3 adjusters by equal amounts - thus moving the secondary back down the tube. As long as you keep tightening the 3 adjusters by small equal amounts each time, you know the mirror base will remain parallel. Keep going until the mirror is at the correct distance down the tube, and do a final rotational adjustment so that the secondary appears completely concentric in the Cheshire. Make sure you don't over-tighten the 3 adjusters at any time. They just need to be finger-tight. Once the above is done, you can remove the paper and start the final tilt-adjustment of the secondary to align it with the primary. Then it's just the standard alignment of the primary.

When adjusting the spider vanes, you need to make sure that the central screw in the secondary holder is equidistant from the tube edges in all directions. You don't need to use them to align the secondary in your scope. As long as the base of the mirror is parallel with the part that the adjusters are in (I'm not sure what you call this bit) it should be reasonably aligned with the focuser, once you have the distance up/down the tube correct. Then you fine-tune it's position under the focuser using the 3 adjusting screws. The 3 adjusting screws should be roughly at the same level. If they are very different, it might be worth trying to get them level before going any further.

That's pretty normal when you are far out-of-focus. Can you get it to focus OK?

What problems have you been having?

I think a quick pic/vid of what's happening would help.

As Ed says - you need to make sure your camera/eye is central. So a collimation cap will help. A Cheshire moreso, as you can get the outer 'circle' closer to the secondary and check concentricity that way. If you are just using a collimation cap, you can use 'Mire de Collimation' to check how everything is centered against your smartphone pics: But it's quicker/easier with a long Cheshire acting as a sight tube:

I have it on SkySafari - but it's the plus version.

Stargazers Lunge! 🤣🤣 Worth starting with this thread. I think it's worth being made into a sticky one: https://stargazerslounge.com/topic/362519-would-uhc-filter-help/

The F5 6" is a table-top dob, isn't it. I notice that the 6" planetary doesn't have the nice Hexafoc focuser that adorns the 8" and 10"

If you turned the secondary assembly and spiders 90deg in that photo, wouldn't that align the adjusters as you want them?

Yep - Edinburgh here. The summer's observing is limited, but worthwhile. Forget anything dim, though. In mid summer, even around 1am, it's still light-ish. But June and August get reasonable darkness that late. Planets are the main targets, but double-stars are good too. The moon obviously, although it is low in the summer. This summer gone, we were treated to comet-hunting with binoculars!

You won't see much more than a blur, even with a larger scope. Darker skies will help. One of the brightest large DSOs is the Orion Nebula. Have a read of this to get an idea of what many DSOs will look like.

SkySafari Plus shows this:

Hi, Have just taken possession of this EP. I realise that it won't be suitable for my fast scope, but thought it might be worth hanging on to. Any pictures of old Celestron or Vixen 2" Erfle look a different to this. I can find similar looking Celestron Erfles, but they are 1.25" Any knowledgeable folk out there able to share some info on this EP?

Just managed to catch the conjunction before the clouds came in. Had to stand on a garden table to get a good view over the wall. All 3 just about squeezed into the field-of-view, 5.5 deg. Dragged the kids out to see it, telling them it'll be years before they'll see it again. Standing on the table appeared to make it more exciting!

Hi, Regarding the stage after removing the paper: One thing to be aware of, is that with a Cheshire, you don't have to bother with trying to get the primary clips equally visible within the secondary. You are trying to centre the image of the primary within the secondary, so instead just adjust the secondary so that the doughnut (radioactive symbol in your case) on the primary is directly under the crosshairs in the Cheshire. That's the whole point of a Cheshire and isn't made clear in Astrobaby's guide. I also think that you might get away with a slight rotation of the secondary - but try the above first.

Isn't Santa going to have to test it first?