Eastridge

Talking theoretically, I would have thought it was just the sort of thing that 3D printing was designed for.  Quite a simple shape and single colour so even a basic printer would be able to do it.  But low volume as they are quite variable as you say.

As a business model you would buy the design online and download it, then print it off locally either at home or a local print shop ( in the way we once went to a shop to get photocopies done).  Think of all the postage, travel miles, packaging , CO2 etc. saved.    

Hi,

Agree that your 25 looks nothing like my 25 MA ( which is exactly as per pic given by Rick above) The 10 is difficult isn't it? doesn't look exactly the same as either MA or Possl pics to me. I guess needs someone with greater experience of lenses to comment.

Hi, can't help with the 25 but I asked about the 10 a while ago and the best answer I got was from Robin ( who did Swindon link above) who said:

The sw ep is not a plossl but an MA (modified acromat) so don't judge the eye relief by the plossl design, the eye relief on the 'super MA' is actually better, I can only guess from my experience, I think it is around 10-12mm, ....

To which Naemouth helpfully added that it's more usable to many others of that length because the image is formed very close to the lens and so even 8mm ER would allow you to see it with glasses.

Hoope this helps

Hi, those who have the 'standard issue' Maplins case is that the Large one ( 460 x 350 ) or is the small one ( 330 x 290) sufficient. The small one would do fine right now ( 4 EP's + some bits) but I am sure that I wil buy more stuff.

A 5mm will give you 254x magnification, which is the theoretical optimum of the scope. Whether the skies can handle that is another matter. I use that magnification on good nights quite a bit (using an 8mm in my 8" F/10). On less good nights, I stick to 203x (10mm for me, about 6.3mm for your scope).

The exit pupil for a scope of F/5 is 5mm for a 25mm EP. A 30mm yields 6mm (exit pupil = focal length of EP / focal ratio of scope). Note that there are big inter-individual differences in pupil diameter. I tend to stick to 5mm because the background stays darker. At 6.7 mm pupil (80mm F/6 with 40mm Paragon) I feel the background sometimes looks washed out. At 5.1mm (same scope with 31mm Nagler) the view is better.

Thanks thats very useful.

Thanks OP, we have just gone for SW250 Dob without GOTO as it seemed to me that for our purposes it wasn't the 'magic' solution that was advertised, you seem to have confirmed that. I'd have had it if it were a cheap option but it's not.

Good info. Thanks for posting.

Another vote of thanks for this. Can someone validate my application of all this great info. to our specifics.

We are getting a Skyliner 250 / 10" which will come with usual 'adequate' quality 10 & 25 & 2xBarlow.

It is f5 Dob so we should look to add somethng c. 7mm ish for maximum magnification?

The Exit Pupil stuff I am less sure of - we are aged 46 & 51 so our age related figure is just over 6, i presume we work on 6 as it will only deteriorate over time. Is the 25 still the one for 6, or should we go for something in the 30's?

So, if we say 7 (to buy), 10 (got), 25 (got) , 30 ish (if required).

Would people upgrade the 10 / 25 first or buy the 7 first?

There is a gap 10 - 25, is that significant, would people get something 16ish?

Looking to view planets and DSO's.

Thanks for any thoughts.