Hello, introduction and help, please.

[Capt Slog]

Hi.

 

I've lurked here for a little while, mainly getting passive advice and learning because I wanted to buy a telescope.

I'm not an absolute beginner, I used to be a physics technician and have assembled and used a few telescopes as part of my job.  From small Meades to 500mm diameter, and even a small radio telescope.  Although I knew the nuts and bolts, I didn't know quite what all the numbers meant so I came on here and it's been very helpful, so thanks very much.

After a  month of looking and missing a few that I thought I would like on ebay and Marketplace, I managed to snag a Skywatcher 150 f750 on an EQ mount (looks a bit like what is now labelled an EQ2-3 , complete with polar scope), and this was for the princely sum of £60.  It came with just one eyepiece, a 10mm.

It was obvious with just a glance that it was way out of collimation , it looks as if it had been picked up by the spider at some point because on of the vanes is bent..  I adjusted the screws on the secondary to the point that I could use it and that night I went out into the garden to try it out.  To my delight, it worked quite well.  The first target saw Saturn, and I thought at first I couldn't focus properly beacause I had an oval in the eyepiece, and then I realised that I was looking at the rings (doh!).  Mover onto Jupiter, counted four moons even through the hazy cloud and low elevation.

Then the moon came up, FULL, so I had a look at that for a while (ouch), and then moved onto directly above me with my remaining eye! Yep, this is what i expected and I think I will have some fun with it, and i do love a bargain.  I've already taken delivery of a 20mm EP, and will build from that.

 

Anyway,  I'd like to know a bit of detail about this telescope, especially what lies under the cover at the mirror end.  I'm loath to remove anything just yet, because it does work, and I can use it, but what am i looking at?  Are those 3 silver screws for collimation, or is there more to do behind that cover?   

Next the spider.  Leave it alone on get right?  At present the  plane of the centre boss is not at right angles to the axis of the tube and the secondary mirror position just looks a bit odd.

Thanks for reading this far, and I hope my pictures work.

 

 

 

Edited October 3, 2020 by Capt Slog

[laudropb]

Hello and a warm welcome to the SGL. If you carefully remove that base plate you will get access to the the Collimation screws. There may be 2 sets of 3 screws. One will hold the mirror cell in place the other will allow you to adjust the mirror to align the optics.

[Starwatcher2001]

Hi Capt and welcome aboard SGL. Glad you like the place.

"... with my remaining eye!" - sounds like you've worked with lasers in the lab too.😀

That's a nice scope you've got, especially for the price. Nice one.

Personally I'd have a crack at straightening the spider vane. It would annoy me "as is", but may damage the image a bit, although I'm sure somebody more knowledgable than me will confirm/deny. Looks like it readily comes out and would probably straighten nicely in a vice. You'll probably have to realign it when you've reassembled it.

With the spider out, I'd have a look at that white part on the focuser tube. Looks like it might be a label with a barcode on. It's in a prime position to reflect stray light into the eyepiece. I'd remove it, or paint it matt black.

Can't comment on the collimation of that scope as I've never seen one in the flesh.

All the best,

Mark

[Aramcheck]

Hi Capt. Slog,

Welcome to the SGL! I found Astro-Baby's guide to collimation to be very useful:- http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/

Cheers
Ivor

[Capt Slog]

Thanks for the replies.

Yes, I did work with lasers too 

I get the feeling that those 3 silver screws are the collimator adjusters, don't know if that's right, just a gut feeling that I'll have to try out.  I found a pic of one apart...

from here   https://www.skyatnightmagazine.com/advice/how-to-clean-a-reflector/

But I think that might be bigger than mine.

I liked the collimator instructions from Astro Baby, thanks for the link.

Ah yes, and that bar code (good spot) is actually a piece of plastic for the focuser to bear against inside the tube, maybe ptfe.  I don't think i can remove or cover it.

 

Today I've made a box to fasten to the inside  wall of an outbuilding to store the telescope in.  I seen that people have to wait telescopes to cool so I thought if it was 'outside' but dry, that would do the trick.  Is that right?

(excuse the mess, I haven't tidied away yet)

 

Edited October 4, 2020 by Capt Slog

[Neil H]

Hi and welcome i had the skywatcher 150/750 a great scope still miss it its on the old eq3/2 tripod rock solid mount i did all the mods on mine before i sold it on . Flocked it inside fitted springs to the main mirror so collimation  was easier made some wilcox rings so i didnt need to balance it in the mount every time as it will only fit in the one place in the rings these also let you spin the scope so eyepiece is always in a great position 

I had some really nice views  from that scope your need some better eyepieces and barlow later on 

That was a great price for that mine did not have the polar scope and you cant get them for love or money it would cost more than you paided so you done really well 

The 3 little screws at the back just hold the cover plate on the back once removed you can get to the collimation screws and locking screws the grub screws are the collimation screws the bigger screws lock the mirror tight dont over tighten them 

As the guys have said already use astrobaby guide to collimation  and your be spot on 

Had a closer look at photos the rings have a dove tail so some one has up graded the mount which is even better for you still make wilcoxs rings tho this lets you have the rings loose so telescope can spin but not go out of balance 

Edited October 4, 2020 by Neil H

[Starwatcher2001]

That cupboard you've made for it looks the biz. Just needs a table with a copy of Sky & Telescope and your scope will be cosy and comfortable 😀

A shower cap over the business end of the scope will help stop other spiders getting in.

I'd avoid putting the scope in there immediately after a session if it's dewed up, let it dry out naturally first. Maybe worth putting some silica gel in there somewhere to absorb any residual moisture.

[Capt Slog]

Thanks, Neil H.  That's just what i needed to know.  Not heard of Wilcox rings, so looked them up.  Wow., They look impressive and i can see the point, they also look expensive and perhaps beyond my diy skills on the lathe.

Thanks, Starwatcher2001.  I did wonder about the moisture, perhaps I need to bring it indoors after a session and then store it after.

 

I didn't mention in the original post, but I actually got TWO scopes for the £60!  This was the other one....

 

[jonathan]

+1 for the flocking, I did mainly opposite the focuser and around the edge of the secondary (the thick glass edge).  You could of course just flock all of the inside but I didn't want to go that far and have to bother removing the spider, but as you might have the spider out anyway...  You could also attempt the inside of the focuser tube, just make sure it's not going to be in the way of any moving parts.  Do plenty of dry test fitting.

I used a vacuum cleaner with curtain attachment to gently pre-remove any loose hairs from the flocking sheet before fitting, though I'm not sure this would be strictly necessary if buying the proper astronomy stuff.

You might want to get a dew shield too, or make one from some thin camping or yoga mat.

I think the black screws around the edge of the base will be holding the rear cell and mirror in place, you shouldn't need to remove those to collimate.  Shine a torch down the tube and check if the mirror is clean. 

Edited October 6, 2020 by jonathan