Pixies

Hard to see from that picture, but are there 2 slow-motion controls? These are the long flexible rods with a knob at the end. I can see one but not the other.

Penultimate!

Yes - Awesome Astronomy gets a vote from me. I'll check out Actual Astronomy too. Cheers.

Sorry - one final comment for the OP. You don't have to worry about the offset. If you follow Astro Baby or the Seronik guides or any instruction using a collimation cap (or Cheshire or sight-tube) when aligning the secondary, it just works. The only time you would need to worry about it would be if you were building your own secondary mirror holder.

OK. here you go. The issue is that when you intersect a cone, the ellipse is not centred over the axis of the cone. If you imagine a cone of light from the primary up towards the secondary, you will either need an oversized secondary mirror to capture the full area of the intersection, or an offset elliptical secondary. Follow this link and find the interactive diagram at the bottom of the page: https://www.geogebra.org/m/NnxHw6gY If you rotate the image so that you are looking down the axis of the cone, the elliptical intersection is offset.

Hi. have a look at this:

That's fine. You are looking at the silhouette of the secondary mirror (the dark circle). The smaller grey circle is the reflection of the underside of the collimation cap. The secondary mirror has what's called an 'offset'. It is supposed to be extended in one direction away from the focuser. It's hard to describe what the offset is for without diagrams. I'll try and find a good article.

Ta. Had to find the new stream

Has everyone else lost the feed?

I think this video is going to become very popular, pretty quickly. Well done!

Here's my review of the FLO Premium Cheshire:

Hi. You need to do the secondary first. Initially you align it under the focuser, then you align the secondary to the centre of the primary. You may find thatthese are already OK. Once that's done you can align the primary mirror. See the following: http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/ https://garyseronik.com/a-beginners-guide-to-collimation/

Just noticed that there's a "Members Equipment Reviews" section. Mods - please feel free to stick this in there if necessary. Cheers

Hi. I bought a pre-loved FLO Premium Cheshire the other week. I have a shorty cheshire but find that very difficult to use as my short-sightedness means I can't focus on the cross hairs or the doughnut at the same time (with or without specs on). Also, the shorty is no good for aligning the secondary under the focuser on my scope, as it didn't get close enough to the secondary. So I bought the above from @Rustang (cheers). And last night was the first chance I had to try it out. It all went well, trying to align the secondary. This cheshire doesn't have a 'shoulder' on the tube, so you can insert it as far in or out as you need. With my Bresser 8" dob, the focuser is pretty deep, so I had it fully inserted and the focuser pretty much nearly full out. This stage of of collimation was nice and easy and quick. Firstly with the focuser racked out for reference and using Astro Baby's coloured paper tip: and moved in closer to make sure it was all aligned: And once that was sorted, the paper was removed and the secondary aligned with the primary doughnut and then the primary aligned so the eyehole was centred in the doughnut: This last image isn't great, the eye-hole is small and it's really hard to line-up the camera lens with it. But in my eye it was sorted. Well - sort of. Aligning the secondary with the primary centre by making sure the crosshairs were over the doughnut was still a little tricky because of my eyesight. But I got it as close as I could then borrowed by daughter's eyes to confirm it was aligned. Aligning the primary was easy with my specs on. So all fine, and I can recommend this cheshire. BUT, there's one drawback. It's because of the finish of the angled reflective surface. If you want to adjust the primary in the dark with a red led torch, there's a problem. The surface is so reflective, there is a specular reflection of the led, which makes it really hard to see the eyehole centred in the doughnut. You see a 'line' rather than a bright circle. My old shorty cheshire has a rough angled surface and the reflection is diffuse: FLO Premium: Shorty: So I will be keeping the shorty in my case for night-time primary collimation. It's a shame there's this one problem with it, when everything else with it is great. It's a well made piece of kit and will last a life-time. If I could suggest one other improvement, a small rubber eyeshield, like with the shorty, would help with the glare when holding up a torch to the side-port, close to your face. 10/10 for indoor full collimation. 2/10 for night-time primary collimation.

That's the 'big-thing-point' about dobs. You are only paying for the optics. The AZ pronto mount and tripod is probably one of the cheapest decent commercial AltAz setups I can find. It's cheaper than John's options (esp the Vixen). However, if you have a sturdy photographic tripod already, you can use that with a suitable AltAz mount. Hang on - that's @John - he's changed his picture. It's so confusing...

If you can work out what thread it is (say 'M4'). You can search Amazon for: M4 knurled thumb screws and hopefully find something suitable

Yep. A friend has it on one of these: https://www.firstlightoptics.com/alt-azimuth/sky-watcher-az-pronto-alt-azimuth-mount-tripod.html

Just out of interest. How does one collimate an SCT with a Cheshire? What do you see when you look down the tube?

I was going to say about using a cheshire as a sight-tube to align the secondary under the focuser. But Jonathan is talking about an SCT. I'm confused now! Don't get me started on the FLO 'premium' cheshire. I'll be doing a review later. There is an issue with the red torch approach!

If it's the 150p and 200p skyliners you are talking about, be aware that the 150 is still the same height as the 200! It's a 'slower' scope at f7.8. The 200 is f5.9 The majority of the weight is in the base. Which is similar for both, too.

Outside in clouds is great (daylight obvs ) If the mount can hold it still, it'll be fine. You could even place the scope on a pillow on a table.

Yep. Who wants to lift their bottom off the stool?

So is it ?: New Televue Bandmate Oiii > old Lumicron Oiii > Astronomik Oiii > Latest Lumicron Oiii > Baader Oiii > 'transition' Lumicron Oiii

The ones going in, in Edinburgh are much dimmer. They won't reach this side of Edinburgh until spring next year. Unfortunately, there are already complaints that they are too dim and the council has agreed to raise the levels once everything has been completed. It does seem as if they have control of the lights centrally. That bodes well for future fine-tuning. Perhaps I could contact the council and ask them to dim one in particular! Also, as Edinburgh does not have any streetlights that go out during the small hours, perhaps now there will be an opportunity to be able to do so?

Before: and after: Unfortunately, I have now allowed more light from the streetlight into the garden. Swings and roundabouts....