TheSkySearchers

I just recently purchased the above scope, it is in very good used condition. I have an issue with it that seems difficult to resolve. Basicially it seems that when looking at astronomical objects its very difficult to move the focuser in enough to bring the object into focus. I have partially solved the problem by substituting an Altair star diagonal in place of the original Meade one. This works with rather more eyepieces but there are still quite a few that won't come to focus. There isn't a problem with the optical alignement, when things do come to focus the stars are pin point across the field of view and the Orion Nebula looks fantastic. I use a mixture of Vixen, Skywatcher and Orion eyepieces. I don't have any Meade 5000 series eyepieces though one is on the way. This behaviour is almost as though the scope was designed for terrestrial use. Does anyone have any ideas or comments please?
Thanks!

i'm not much of a visual observer, it's pretty normal to have different focal zones for different brands and types of eyepieces , you can buy parfocal rings that you lock onto the eyepeice, about $10 a piece ,this will keep all the eyepieces at the same focal position once calibrated .

https://www.amazon.com.au/Astromania-Te ... 9BHI&psc=1

i don't know the scope, so i'm unfamiliar with the stock eyepieces and daigonal that come with it, so you'll have to wait for a recomendation on a good low profile diagonal from someone else if needed .

Thanks for your interest and reply. My probem is the lack of inward (towards the objective triplet) movement. Those eyepieces that work come to focus at very similar positions on the focuser its just that there is little further inward focus to accomodate those that don't work. I'll do some resarch on low profile diagonals, hadn't thought of that, good idea.

There appears to be some consensus that a prism diagonal may improve thinks by up to a 3/4" but they are pricey so I'll test with the 5000 eyepiece when it arrives before making a decision.

Welcome to TSS John! The only way to gain inward focuser travel is to use diagonal with shorter light path (or no diagonal). The shortest light path would be 1.25" prism diagonal.

In your first posting you do not say if you are using a 2" or 1.25" diagonal?
I may have missed that though.
A 1.25" mirror diagonal may work if you are using a 2" diagonal, if not the next step is a 1.25" prism or there is a eyepiece adapter that lets you get about 10mm more inward travel though it is only good for 1.25" eyepieces.

Thanks again for the replys, an altair 2" prism diagonal arrived this morning as did a 9mm Meade 5000 series eyepiece. I'll test the eyepiece with the standard Meade diagonal first, then try the Prism diagonal. Will post with results when I have them. Fingers crossed for clear skies.

By the way I was using a meade Series 5000 2" mirror diagonal. I find it a little puzzling that an astronomical telescope should be designed in such a fashion.

Has the focuser been changed on the telescope?

No, the focuser is the standard meade one. I did think of changing the focuser but it is rather a pricey step to take beofre trying all the other options.

My thought was that someone changed it and this was causing the issue.
Has the prism helped?

Prism v Mirror diagonal results. The following assumes the calibration marks on the Meade focuser tube are at mm intervals

Using the Meade 5000 series 2" Mirror diagonal an Meade series 4000 - 40mm eyepiece came to focus at 3mm from inward dead stop.
sing the Meade 5000 series 2" Mirror diagonal an Meade series 5000 - 9mm eyepiece came to focus at 6mm from inward dead stop.

Using the Altair 2" Prism diagonal an Meade series 4000 - 40mm eyepiece came to focus at 6mm from inward dead stop.
Using the Altair 2" Prism diagonal an Meade series 5000 - 9mm eyepiece came to focus at 14mm from inward dead stop.
Using the Altair 2" Prism diagonal an Svbony 10 - 30 mm zoom eyepiece came to focus at 14mm from inward dead stop.

I didn't test the Svbony with the Meade Diagonal.

The Altair Prism Diagonal is a definite improvement and will probably prove satisfactory in use. I will not come to any conclusions about the series 5000 eyepieces until I have at least one more to test with although early indications are promising!

Thanks for the support, I mau update this in a week orso.

Altair 2" prism is a high quality diagonal, optically and mechanically. I have been using one for a couple of years.

Glad to hear that, I'm planning to stick with it! I have an Altair Mirror diagonal for use with my starwave 80ED doublet, I may sell that and buy a 1/25" Prism diagonal for useinits place, w'll see.

I have just won a 25 mm meade series 5000 on eBay, when it arrives I'll add the results to this list just for completeness!

johnyjf wrote: ↑Sun Jan 22, 2023 11:09 pm Glad to hear that, I'm planning to stick with it! I have an Altair Mirror diagonal for use with my starwave 80ED doublet, I may sell that and buy a 1/25" Prism diagonal for useinits place, w'll see.

If the mirror diagonal works with your 80mm I would not bother buying a second prism.
Prisms to not always work with every refractor and can degrade the view if not compatible.

Is your Altair mirror diagonal standard of premium version? If it is premium I would keep it. But getting a good quality 1.25' or T2 prism is a good idea.

I think the diagonal is the premium version it has "Enhanced 99% reflectivity" printed on it. AS for the 80ED I have a 1.25" Televue diagonal that I'll try before buying anything else. The new 25mm Eyepiece should arrive by Monday so fingers crossed for clear skies.

I recently purchased a used Stellavue 102ED f6.95. Almost identical specs.

It has an after market, 2" x 50mm long body, Feather Touch focuser.

I can get
all my eyepieces to focus with a GSO 2" quartz mirror diagonal,
camera to prime focus.
Use a Televue 0.8 X reducer flattener, I don't have enough in-focus.
A non-reducing flattener works fine.

If I ever want to use the reducer, I need to cut the tube down. Grrrrr!

Joe

My sympathies, I'm tempted to fit a Baader diamond track to my 102ED but I'm worried it may make things worse, need to take a few careful measurements first. Incidentally I had 10 years ago I believe) a Stellarvue 90mm flourite which I regret selling to this day. I'msure your scope will be very rewarding visually.