90mm ED Refractor

[sojourneyer]

I have always felt that a 90mm was an optimal scope for lightweight grab and go purposes. 

 

A 102ED with rings weighs in the area of 12 lbs which is too much for many lighter weight mounts to handle.

By lighter weight mounts I am alluding to the Versago, smaller Twilight, etc mounts.  If you add a 102ED for example to a Twilight I you are talking about 30 lbs plus.

 

A 90ED would be  easily under 10 lbs and with some of the smaller mounts the total weight would be under 20 lbs which is great for a quick grab and go viewing at night.

 

Do you think that there is a market for a reasonably priced  90mm ED in the low $500 range? 

[Louis D]

Possibly, but it seems most folks jump from 70mm or 80mm to 100mm for their second scope if staying within ED scopes.  Not many make the jump to 90mm without expecting a massive improvement in optical quality to compliment the subtle increase in aperture.  That's what I was doing when I went from a 72ED to a 90mm FPL-53 triplet.

You're right, it's a great grab and go or travel sized scope.

[RobertI]

I think there are a few fast 90mm refractors around like this one from SVBONY. Doesn’t say what kind of glass, could be quite a bit of chromatic aberration given the focal ratio and price, but should be very portable, eg: for airline travel.

But my 102ED F7 sits on an AZ4 mount (like the Versago 2?) and it’s a very stable setup, which is also nice and easy and quick to set up in the garden, so is very grab and go in that sense. 

[John]

The William Optics Megrez 90 was a nice, light, compact 90mm ED doublet. It's new price exceeded the budget stated but on the pre-owned market you might be able to hit it for that. If they made it with FPL-51 glass the retail price may well have been something like $499 but at F/5.9 the small amount of CA that would show might annoy some. There are scopes of that type about but they all seem to have much higher prices eg: the Tele Vue 85, AP Stowaway, Baader 95mm etc, etc. Burgess Optical made a cemented 91mm ED doublet for a while I recall. I don't know how they were priced though ?

 

Edited September 4, 2023 by John

[sojourneyer]

1 hour ago, RobertI said:

I think there are a few fast 90mm refractors around like this one from SVBONY. Doesn’t say what kind of glass, could be quite a bit of chromatic aberration given the focal ratio and price, but should be very portable, eg: for airline travel.

But my 102ED F7 sits on an AZ4 mount (like the Versago 2?) and it’s a very stable setup, which is also nice and easy and quick to set up in the garden, so is very grab and go in that sense. 

Rob, yes the AZ4 is the same as the Versago 2 but they have those nice thick 1.75" steel legs and that makes a big difference.   Your mount weighs over 18 lbs.

You can not even get them in the States now.  The Versago E weighs only 8 lbs

I have that Svbony Achro and like it for DSO. That is why I wished they had an ED version.

 

Edited September 4, 2023 by sojourneyer

[sojourneyer]

1 hour ago, John said:

The William Optics Megrez 90 was a nice, light, compact 90mm ED doublet. It's new price exceeded the budget stated but on the pre-owned market you might be able to hit it for that. If they made it with FPL-51 glass the retail price may well have been something like $499 but at F/5.9 the small amount of CA that would show might annoy some. There are scopes of that type about but they all seem to have much higher prices eg: the Tele Vue 85, AP Stowaway, Baader 95mm etc, etc. Burgess Optical made a cemented 91mm ED doublet for a while I recall. I don't know how they were priced though ?

 

Thanks,

That nice WO scope weighed only 7.1 lbs without the rings and dovetail. A good weight. Those puppies had costed almost $1100. 

But if one paired up a FPL-51 glass with one Lanthanide glass the CA would somewhat negligible.  Svbony has those two types of glass in their 102ED and users have raved about that scope.   This is where a $500 price point seems realistic.

I am thinking about a scope in the low $500 range not those upper echelon brands of scopes.

 

 

 

 

 

 

 

 

[sojourneyer]

Rob

Here is the 48P (90mm Achro  f/5.5) on the mount I use. (Celestron Starsense Explorer DX)

Total weight as you see it with the Starsense cradle is under 15 lbs.

[sojourneyer]

I just checked and there are a few 90mm ED scopes but they are all APO triplets costing around $1500

[wheresthetorch?]

6 hours ago, sojourneyer said:

Here is the 48P (90mm Achro  f/5.5) on the mount I use. (Celestron Starsense Explorer DX)

I've been considering buying a Starsense DX set up to mount a similarly sized refractor (Opticstar AR80S).  Are you able to reach the zenith without the scope striking the tripod legs? 

[RobertI]

9 hours ago, sojourneyer said:

Rob, yes the AZ4 is the same as the Versago 2 but they have those nice thick 1.75" steel legs and that makes a big difference.   Your mount weighs over 18 lbs.

You can not even get them in the States now.  The Versago E weighs only 8 lbs

I have that Svbony Achro and like it for DSO. That is why I wished they had an ED version.

 

Nice compact setup. 👍

[sojourneyer]

9 hours ago, wheresthetorch? said:

I've been considering buying a Starsense DX set up to mount a similarly sized refractor (Opticstar AR80S).  Are you able to reach the zenith without the scope striking the tripod legs? 

Good question.Funny thing is that 4 days ago I tried such a situation and it could not reach zenith.  Almost .. about a 1/2 " and it would have made it.

All I did was put a piece of wood under the front leg and had the scope so that the other two legs were facing me... The funny thing is that the Celestron 102 that came with it did not have that problem..   If I added a 2 inch extender it would be fine.  What hits the mount base is the focuser

 

Edited September 5, 2023 by sojourneyer

[wheresthetorch?]

1 hour ago, sojourneyer said:

Good question.Funny thing is that 4 days ago I tried such a situation and it could not reach zenith.  Almost .. about a 1/2 " and it would have made it.

All I did was put a piece of wood under the front leg and had the scope so that the other two legs were facing me... The funny thing is that the Celestron 102 that came with it did not have that problem..   If I added a 2 inch extender it would be fine.  What hits the mount base is the focuser

 

Interesting - thank you.  One other question if I may: is the the mount removable from the tripod, to fit on a beefier tripod with a standard 3/8" thread? 

[sojourneyer]

Yes the mount is removable.  You just need to unscrew the legs and  you are off to the races.  you do not have to remove the mounting base.

I will try to take a pic for you later

[sojourneyer]

here are photos for you

I hope that helps

[wheresthetorch?]

3 minutes ago, sojourneyer said:

here are photos for you

I hope that helps

Massively helpful - thank you! 

[sojourneyer]

so you can either remove the legs and keep the mounting base or remove the mounting base with the legs

[Emperor!Takahashi!]

I had a Borg 90FL that was good in its ways but that went up for sale when I bought a Takahashi FC-100DC. The 100mm Tak wasn't much bulkier than the 90mm Borg and thoroughly outperformed it.