Spile

You are welcome Pat

I’ve written a guide which you may find of use. https://astro.catshill.com/collimation-guide/ the Cheshire eyepiece and sight tube combination tool should help you get the secondary mirror correctly placed. From the image you posted a would appear to be the same as b but c does not equal d .

I have the Skywatcher 8” and it’s a great Dob, but if I were buying today, I would go for the StellaLyra

I’ll echo the advice to hang fire on accessories and additional spending. Use the time to develop your skills. In terms of collimation, start with a simple cap as it will get you close. Get to know the alignment of your mirrors through the focus tube. This will help https://astro.catshill.com/collimation-guide/

I like to keep as low tech as possible and the diy shield does a pretty good job on most nights https://astro.catshill.com/telrad-dew-reduction/

Mirrors on my 200P don’t dew up but my eyepieces, finder and Telrad suffer although the Telrad shield does help.

At sunset I managed to show my wife five planets and a great transit of Ganymede including shadow. I went out at half eight and had a fairly good 90minutes and a few favourites and a new and very tight double near Betelgeuse . A combination of cold and dew finished me off at ten pm.

Nice idea, I also use a 5 point rating for targets.

I recommend a cap for aligning the primary and a Cheshire eyepiece and sight tube combination tool for the secondary. You can replace the three Allen keys bolts on the secondary with m4 30mm thumb screws.

Ah I believe I now understand what you’re saying.

No the black secondary silhouette is offset with respect to the bright ring.

Can I put in a recommendation for Castor? Two piercing, bright white diamonds.

First of apologies for any misunderstanding. I am confused because the only thing I have offset in my diagram is the dark reflection of the secondary and that “points” away from the focus tube towards the primary mirror. The bright ring of the cap isn’t offset.

Do give my guide a spin and see how you get on https://astro.catshill.com/collimation-guide/

The red ring is the edge of primary reflection. The green ring is the actual edge of the secondary. The offset secondary reflection (rx3) is dark because it’s the bottom edge of the sight tube. I’ve broken each reflection down here https://astro.catshill.com/through-the-eyepiece-tube/

I would take your time and read a number of guides in order to get a flavour for what is being recommended and for what. Sorry to sound vague but it’s easy to waste money and there are some dangers in buying blind. I’ve put my thoughts here https://astro.catshill.com/buying-telescope-start-here/ However given your budget and requirement for portability, I would be looking at binoculars and a copy of Turn Left at Orion.

The manual should say everything apart from the offset secondary reflection. a b c d e f are what I use in my guide above to identify the distances important for collimation.

Well I am a fan of a zoom eyepiece but I would definitely not recommend upgrading a telescope including eyepieces until you have spent time mastering your existing setup. This is a slow hobby that rewards patience and time.

Refer to the labelled diagram above, the dark reflection of the secondary should be offset in the direction of the primary and as my guide says, this is a useful check. As for the central screw, if a=b and there is no rotation error, tighten it if it’s slack but the push-pull arrangement means that it shouldn’t be. So just work through the three outer bolt’s sequentially and very gradually.

By very very slightly altering the other bolts and working your way round you get all three secure.

Thanks it must have appeared late.

Does anyone know what has happened to the monthly virtual planetarium that Pete Lawrence and Paul Abel put on YouTube? The last one was for December 22.

I may be misunderstanding your point but the “eye” of the Cheshire should be pointed towards a light source and you do this by rotating it in the focuser.

I set up the 12” Dob at the astronomy club this evening as it was a rare clear evening. We had a few refractors set up too. I decided to take along my zoom and we had some nice view of Jupiter including the extremely close Callisto, Mars, M42 and M32, Almach, M45 and the Trapezium, Castor and finished by splitting Rigel. Some very happy observers.