Jump to content

Banner.jpg.692da9ed9af2eace53e1dc94cfc0e912.jpg

Which 2.5mm?


Sunshine
 Share

Recommended Posts

Just finished looking through eyepiece choices online for a good 2.5mm with as wide a field as possible considering I mostly use manual equatorial or Alt-az mounts. To my surprise I found one!  I repeat, one…the Tak TOE but with a FOV of 52 degrees and a price of $500 I was quickly turned off. Am I missing something? surely there are more choices in the 2.5mm range, I have no problem justifying the money but not for 52 degrees, not for a super sharp straw. Some may ask if I have a barlow which I do, a 2.5x Powermate but I’d rather not use it for visual as I hate fumbling eyepieces into Powermate and he whole appendage into the diagonal to end up with a foot long trunk sticking out of my diagonal which to make things worse, throws my alt az out of balance, suddenly. 
 

Anyone know of a 2.5mm fitting my needs? Thanks.

Edited by Sunshine
  • Like 1
Link to comment
Share on other sites

There used to be a 2.5mm type 7 Nagler ie 82 degree afov. Very nice eyepiece, had one for a while. Picking one up used would be the only possibility now though I think.

  • Like 2
Link to comment
Share on other sites

Type 1 4.8mm nagler barlowed? It’s very sharp and wide but only about the size of a 20mm plossl. If you don’t mind tight eye relief… I’ve not tried mine barlowed before but will give it a try next time. 

Mark

  • Like 1
Link to comment
Share on other sites


Ok, you’ve said you don’t like a barlow, and I do understand your objections.

However, everything is a compromise in one way or another.  I do have an original Vixen LV 2.5mm with 45 deg apparent field, the modern replacement SLV has a slightly wider 50 deg field.

If it were me I’d accept a compromise, use a barlow or live with a narrow field.

Long shot- a used 2.5mm Nagler. But that’s a compromise too with 12mm eye relief, or a used 2-4mm Nagler zoom, or…whatever…

Ed.

  • Thanks 1
Link to comment
Share on other sites

1 hour ago, NGC 1502 said:


Ok, you’ve said you don’t like a barlow, and I do understand your objections.

However, everything is a compromise in one way or another.  I do have an original Vixen LV 2.5mm with 45 deg apparent field, the modern replacement SLV has a slightly wider 50 deg field.

If it were me I’d accept a compromise, use a barlow or live with a narrow field.

Long shot- a used 2.5mm Nagler. But that’s a compromise too with 12mm eye relief, or a used 2-4mm Nagler zoom, or…whatever…

Ed.

In that case I’d rather stick with my 5mm XW with my 2.5 Powermate as it maintain the 70 degrees of the XW, as much as I dislike a foot long appendage on the diagonal. It is more power than a prime 2.5 but I don’t think they make a 2x Powermate which would be closer to what a 2.5 prime would give.

Edited by Sunshine
  • Like 1
Link to comment
Share on other sites

1 hour ago, Sunshine said:

In that case I’d rather stick with my 5mm XW with my 2.5 Powermate as it maintain the 70 degrees of the XW, as much as I dislike a foot long appendage on the diagonal. It is more power than a prime 2.5 but I don’t think they make a 2x Powermate which would be closer to what a 2.5 prime would give.

There is a 1.25" 2x ES telextender but the transmission won't be as good as the powermate and you also need to flock between the lens groups to avoid reflections. 

  • Thanks 1
Link to comment
Share on other sites

1 hour ago, Sunshine said:

In that case I’d rather stick with my 5mm XW with my 2.5 Powermate as it maintain the 70 degrees of the XW, as much as I dislike a foot long appendage on the diagonal. It is more power than a prime 2.5 but I don’t think they make a 2x Powermate which would be closer to what a 2.5 prime would give.

There is a 2” x2 Powermate…..

17DE3514-FA84-43FE-8658-C8110C143F80.png

  • Like 1
Link to comment
Share on other sites

I've got a 2.5mm Planetary TMB II Eyepiece on order from China via ebay.  For $35+tax I thought it would be worth a try.  Once I get it, I'll compare it to my 3.5mm Pentax XW and my 5.2mm Pentax XL Barlowed.  It might end up being a project eyepiece where I have to blacken or flock the interior to control stray light if the optics pan out.  If the optics are bad, I'll do an exposé on it here on SGL and write it off as a learning experience.  If I like it, I might get the 4mm version as well.

  • Thanks 1
Link to comment
Share on other sites

18 minutes ago, markse68 said:

what advantage does a power mate give over a barlow at short fl?

 

Main benefit would be that it doesn’t affect the eye relief by pushing it out further. That can be useful if barlowing short f/l length orthos and Plossls, but with an XW that has 20mm already it could be a pain as it might get harder with eye placement.

  • Like 1
Link to comment
Share on other sites

I get very good performance when using a UFF 10 mm barlowed, compared with a TOE 4 mm. The Barlow is placed ahead of the diagonal.
However the stack does become a little long,  but the contrast is worth it…

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.