Should I buy this?!

[Baskevo]

Stellarvue 80mm FPL-53 Triplet APO

Found it used on Astromart for $800. What do you guys think? I am currently using a ES 80mm Triplet FCD100 with 2.5" Hex focuser--but the lack of a dedicated field flattener drives me nuts.

And I really like the rings that come on this scope... I could get rid of my side-by-side set up, have less weight on the mount.

[Mac]

Looks like a great deal, less than 1/2 the original retail price.

You can't find a FF that will work on the ED80? I am still looking for a reducer for my ED-102 and with the smaller sensor of the ASI533, my field is flat

Do it James, you know you want it.

[Baskevo]

Haha I have decided I would totally do it, but I think someone else will buy it first... I'm going to bed just right now (at 7am) and so I probably won't see a message from him until after he's sold it to someone else We shall see!

And no, I cannot get a flat field on my ES 80mm. Here's the story behind this:

Keep in mind, I want my images to have the best looking stars, which is just a personal preference... If I see any sort of elongation, even if others don't, it bugs the hell out of me. I'm hesitant to tell the story of flattening my field because I don't want others to think its okay to become obsessed with having a perfectly flat field lol if someone is happy with their images, even if theirs a little elongation, chances are high that no one will notice except for the photographer...

I started AP last August with a regular Explore Scientific 80mm triplet APO refractor. I spent about a month trying to figure out why my field flattener was a) giving me wonky stars and b) not giving me nice round stars near the edges. So I sent that flattener back, tried the same 2" ES field flattener, with the 55mm back focus. My stars weren't wonky anymore in the middle, but I was still getting elongation toward the corners. I tried spacing up to 60mm, and could not get it to work.

So I tried some other flatteners... I tried the Orion 2" FF and the Hotech SCA Field flattener, and it was the same thing. I sent those back.

Sometime around then, I forget if it was before or after I tried the different brand of flatteners, I decided to upgrade to an 80mm FCD100 with the 2.5" HEX focuser. I hoped it was the scope, because I knew it wasn't the flattener, and I had tried 3 different cameras with the scope at this point (t3i, t7i, and ASI1600mm pro). But it was just my luck that it was the same thing. Someone suggested that I try even more spacing with my ES field flattener, so I did.

It looked 10x better with around 80 to 90mm of total spacing (25 - 35mm of more spacing than the required 55mm). While it was still not totally flat, it was a lot better than it was. I was satisfied for a little bit, but as a perfectionist I eventually decided I want to improve the flat field even more... I ended up having to return my first FCD100, and received a brand new one (which I had to replace AGAIN as soon as it arrived from cracked glass or something...), but it was the same thing. Required 80 to 90mm of total back focus, with still not a perfectly flat field.

So now, I am using a blue fireball manual rotator, and have it fully threaded with another Hotech SCA Field Flattener. At first, the 55mm recommended back focus didn't work, so I decided to try an extra 20mm. Much much better. Even better than the ES flattener. It seems to be helping, but it varies between subs. Some frames look perfect, other frames have an uneven flat field (elongation toward the left or the right). so I think it has something to do with the focuser maybe? Or it could possibly be tilt... I have no idea. I also think it is better when my guiding is excellent, but I could be imaging that.

I purchased a laser collimator to try and collimate my focuser, just haven't gotten around to doing it yet. I hope it is the focuser, because if I end up not upgrading my scope, The only other possibility I can think of is tilt in all 3 of my cameras...

[Mac]

Haha I have decided I would totally do it, but I think someone else will buy it first... I'm going to bed just right now (at 7am) and so I probably won't see a message from him until after he's sold it to someone else We shall see!

And no, I cannot get a flat field on my ES 80mm. Here's the story behind this:

I often feel ' why does this happen to me ' and don't feel so alone after reading that.

Sometimes being so pedantic can come back and bite you in the a$$ and the pocket book. My first ED-102mm had chipped front glass from B&H, pretty sure they sold me someone else's return and hoped to get away with it.

Good luck and good night/day!

[Lady Fraktor]

Good luck you are going to enjoy the Stellarvue when it arrives.

[Baskevo]

So the seller got back to me! I'm a little nervous though. Does that price seem low?

The scope is 8 years old, purchased in 2012, which I don't know how I feel about that. He says it has the best views he's ever had from it. He is selling it because he got selected for the purchase a specialized scope.

What do you guys think?

[SonnyE]

I think buy it.
And if it turns out to be a pig in a poke, sell it.

I would check the history.
Like did they make a fluorite telescope in 2012? :Think:


It's your money. Use it when you need it.
Only you can decide.

[Baskevo]

Well how would I find that out? Lol

You know what I think I could probably do...

I could sell my ES 80mm FCD100 with my stepper motor, and Canon t3 + batteries + case...

80mm: $700 - $800
Field flattener - $100
Stepper motor - $300? (I paid $600 for it I think, and that was like a month ago)
T3 w/ accesories - $200 - $300

that's 1400 toward a new scope... I could buy the SV new! But I would want to get a stepper motor for that one... but maybe there is a cheaper alternative like the EAF. I would also need the dedicated field flattener... Ugh this is so complicated but it sounds worth it.

[bladekeeper]

As an owner of both Stellarvue and ES scopes...I say do it.

[Lady Fraktor]

BUY IT!!!

It is a good price for the size and the fact it is a triplet.

[Baskevo]

BUY IT!!!

It is a good price for the size and the fact it is a triplet.

Should I buy the used one or should I buy it new and sell my current gear?

[Lady Fraktor]

That would be up to you but you can sell the ES 80mm as you will not need it anymore
The new Stellarvue will have a higher Strehl and have that new refractor smell! At $1600USD for an SVX it is a good deal either way you go.
(The older SV will probably have a higher Strehl as well)

[Baskevo]

That would be up to you but you can sell the ES 80mm as you will not need it anymore
The new Stellarvue will have a higher Strehl and have that new refractor smell! At $1600USD for an SVX it is a good deal either way you go.
(The older SV will probably have a higher Strehl as well)

Why would the older refractor have a higher Strehl? each time I am about to say I'm going to go with the older one, I get a feeling telling me not to do it... I don't know why, but I wish it would go away lol

[Lady Fraktor]

Better glass and Vic used to cherry pick these older lens sets to get the best ones, all the other would get sent back.

[Baskevo]

Here's a thought... I'm doing research on differential flexure, and found this website:

http://astronomy.mdodd.com/flexure.html

the second image is almost identical to what some of my frames look like with the ES 80mm. Could the focuser sagging or moving cause elongation of the stars on one side of a sub? Or would differential flexure affect the entire image?

I think another issue is that even though I am using a side-by-side setup, my guide scope is still in 3-point rings... I don't know how else I could fix the 50mm guide scope to the dovetail without the rings tho.

after doing some research on the scope, it looks like the SV also has some focuser issues... I don't know if it would be worth it.

[JayTee]

I have had that very problem. Because I use a cheap refractor with a plastic focuser as my guide scope, I had to put an additional screw in the focuser housing to lock it in place and keep it from sagging. Before the locking screw was in place I experienced two different effects: one was a shifted image when the focuser dropped a significant distance and then there was a more subtle effect that as it gradually sagged it elongated the stars.

JT

[Baskevo]

I have had that very problem. Because I use a cheap refractor with a plastic focuser as my guide scope, I had to put an additional screw in the focuser housing to lock it in place and keep it from sagging. Before the locking screw was in place I experienced two different effects: one was a shifted image when the focuser dropped a significant distance and then there was a more subtle effect that as it gradually sagged it elongated the stars.

JT

I've been experiencing that! Would a solution be just a better guide scope?

[JayTee]

That, or just beef up the focuser. That's what I did and it works fine now.

[Baskevo]

That, or just beef up the focuser. That's what I did and it works fine now.

I'm bad with stuff like that... Lol I've been wanting to get a new guide scope for a while now. Any suggestions on a good one? It is hard to find a 50 - 60mm guide scope that doesn't have tube rings

[Baskevo]

The price just got reduced to $600 :O