APM 2 inch Erect-Image-prism with fast-lock

[Doc]

Father Christmas was very nice to me and bought me an APM 2 inch Erect-Image-prism with fast-lock.

http://www.apm-telescopes.de/en/optical-accessories/stardiagonal-mirror--prism/apm-2-inch-erect-image-prism-fast-lock-ultra-broadband-coating

According to the product information on the website the diagonal has a full 46mm of free aperture, the most ever developed. 

Well tonight is meant to be a clear night so fingers crossed I can give a test and of course I will let you know what it is like. But in the meanwhile I can say thet it arrived in a very nice sturdy white box, which was padded with styrofoam type of material. The diagonal itself feels very well made and oozes quality. It feels weighty and the click lock system works very well indeed. 

While setting up today I compared both my Skywatcher and APM on a distant ariel and I can confirm that the APM diagonal needs 11mm of in travel of the focuser to come to the same point that the Skywatcher focused.

Anyway here's a few photo's to wet your appertite.

 

[Doc]

I had a 3 1/2 hour session tonight and it took a little while to get used to it but I must say I'm pretty impressed. On the moon it was fantastic, in my opinion it didn't degrade in any way. I got out my Rukl moon atlas and I followed certain areas of the moons surface and it was so easy to follow as everything is the correct way up. 

Star hopping was also dead easy, I used Skysafari and found a lot of dim objects such as the Eskimo Nebula with ease. I can't believe how much easier star hopping is without the need to think which way I need to go, left is left and right is right, simples. I managed to find Uranus by star hopping so I'm pretty impressed.

Star colours seem a lot more vivid using the APM Prism diagonal instead of my Skywatcher diagonal. Yellow and red stars really seemed to pop with colour.

I inserted my 2" eyepieces into the both focusers and compared the view and I couldn't detect any restrictions or light loss so I cannot see any reason not to believe that the prism diagonal has less then the 46mm aperture it claimns to have.

There was two negatives the first one was on certain stars like Capella and Procyon I could easily detect a line similar to what a spider vane produces. I've read about this line before and it is produced by the joint in the prism. APM says it is almost invisible and on medium to dim stars I will agree but on bright stars it's quite easy to see. The second negative was brighter stars seemed to be a little bloated compared to the normal diagonal, this was very slight and didn't occur at all on dimmer stars. I'm not sure why this happened, it needs a little detective work to find out if indeed it was the prism or atmospheric conditions.

None of the above observations are completely scientific and I would imagine there are better tests to do, but I don't know them. Overall I'm happy with the prism diagonal especially on Lunar work it was simply fantastic.

[iPeace]

Sounds great! I share your enjoyment of all the advantages.

The two Baader T2 amici prisms I currently have do not show any artefacts on bright objects - but I did return two of them that did! It wasn't horribly bad by any means - a ghostly line extending horizontally either side of Jupiter - but since my first one didn't show this, I reckoned they could find me another. Baader insisted that these variances in performance are within their established production tolerances, which is fine with me as I now have two which to my eyes are perfect. I took from this that it's very difficult to get a correct-image prism produced to a consistently exacting standard - and that I'm a pain in the Aries when it comes to such things.

When it comes to Lunar observation in any detail, any such artifacts are simply not visible and it's all grand.

[Doc]

That's what I thought. I haven't observed any bright planets yet so cannot say what it is like on them, the only one I think I should be worried about is Venus. I'm concerned that if I swapped it, I could get a worse one, then I might get a better one, not sure what to do.

I have nothing to compare it to so I'm in the dark really. I really like the one I got, it oozes quality and performs really well.

[iPeace]

4 minutes ago, Doc said:

That's what I thought. I haven't observed any bright planets yet so cannot say what it is like on them, the only one I think I should be worried about is Venus. I'm concerned that if I swapped it, I could get a worse one, then I might get a better one, not sure what to do.

I have nothing to compare it to so I'm in the dark really. I really like the one I got, it oozes quality and performs really well.

You really like it, so keep it, simples.

I was really lucky with my first one. When the second one was not as good, I thought there must be something wrong with it. Then the third one was just like the second one had been and I began to realize that the recipe for these things doesn't give the exact same result every time. Eventually, The Man at Baader opened boxes for me until he found one as good as the first. This of course involved a lot of friendly, persistent e-mailing, etc.

I was content to go through all this faff because I had the first excellent one safely in possession. In your shoes I would be inclined to keep and enjoy the APM and perhaps gradually over time gently embark on a low-key odyssey to see whether anything better could be acquired. Especially in the 2" format, "pickins are slim" - Baader's 2" offering has been unavailable for years now. Mine are the T2 size and can be configured with a 2" clamp and nosepiece but you're not getting 2" of pipe throughout, so to speak, so that's a compromise if you use 2" eyepieces (I chose to switch to 1.25" exclusively for other reasons).

Even if you only use this one on the Moon, as a Lunar enthousiast (I believe you do dabble? ) what you've got is definitely worth having. You could also consider getting a standard, non-correcting prism diagonal for non-lunar work, which will give you the star colour etc. without the spikes and (probably?) without the bloat. Baader has an excellent 2" model which I really enjoyed using before I passed it on as part of my migration to the 1.25" format.

[Doc]

Exactly the same reasoning and conclusion I've come to as well. I will keep this and maybe invest in a Baader non correcting prism. Thanks for your help I really do appreciate it.

[ollypenrice]

Interesting to know that the moon doesn't degrade in good prisms. I've only tried it in basic ones and found them pretty disastrous. I'd only want one for the moon, really, but this has got me thinking...

Thanks for the review.

Olly

[Paz]

Thanks for posting this review. I'm a visual find-things-manually observer and have kept on using a sky watcher raci diagonal in preference to a mirror diagonal and a tak prism diagonal simply because I get tied up in knots with flipped images both in terms of finding things and in terms of working out what I was looking at after a session, particularly when it comes to lunar features.

I'm going to give my own diagonals another direct comparison in the field to see if I experience much difference in quality (I've compared directly in the past but not under helpful conditions) Unless the quality is noticeably worse in the raci then I'm up for a better quality raci diagonal like this APM, which I am sure is much better quality and bigger aperture than my 1.25" sky watcher.

[Highburymark]

On 28/12/2017 at 11:24, iPeace said:

You really like it, so keep it, simples.

I was really lucky with my first one. When the second one was not as good, I thought there must be something wrong with it. Then the third one was just like the second one had been and I began to realize that the recipe for these things doesn't give the exact same result every time. Eventually, The Man at Baader opened boxes for me until he found one as good as the first. This of course involved a lot of friendly, persistent e-mailing, etc.

I was content to go through all this faff because I had the first excellent one safely in possession. In your shoes I would be inclined to keep and enjoy the APM and perhaps gradually over time gently embark on a low-key odyssey to see whether anything better could be acquired. Especially in the 2" format, "pickins are slim" - Baader's 2" offering has been unavailable for years now. Mine are the T2 size and can be configured with a 2" clamp and nosepiece but you're not getting 2" of pipe throughout, so to speak, so that's a compromise if you use 2" eyepieces (I chose to switch to 1.25" exclusively for other reasons).

Even if you only use this one on the Moon, as a Lunar enthousiast (I believe you do dabble? ) what you've got is definitely worth having. You could also consider getting a standard, non-correcting prism diagonal for non-lunar work, which will give you the star colour etc. without the spikes and (probably?) without the bloat. Baader has an excellent 2" model which I really enjoyed using before I passed it on as part of my migration to the 1.25" format.

I'm with you on this Mike. Even after decades of moon viewing, I still yearn for a straight up, faithful image in the eyepiece. All other targets aren't a problem. Did you buy your T2 amici prism from a retailer, or direct from Baader? Just wondering if i go direct it might be easier to get a good 'un?

[iPeace]

38 minutes ago, Highburymark said:

I'm with you on this Mike. Even after decades of moon viewing, I still yearn for a straight up, faithful image in the eyepiece. All other targets aren't a problem. Did you buy your T2 amici prism from a retailer, or direct from Baader? Just wondering if i go direct it might be easier to get a good 'un?

Got mine directly from Baader. They're friendly enough - a smaller scale operation than it might seem, methinks. Definitely easier not to have to go via a retailer if you're planning to return a few of them until you're satisfied.

[Olle Eriksson]

Hi Doc..  thinking about getting this one too. Would it be too much to ask for if you could measure the length of the nosepiece, the part that goes into the focuser? I know it's not terribly important, but it would give me some piece of mind if I can insert it fully into a very shallow Baader Clicklock 37mm (with 30mm depth for nosepieces).

Best regards

Olle

 

[GlenM]

If you still need to know, it's 36mm.

 

Glen.

 

[Doc]

Oh sorry I should have answered this, for some reason I didn't see the post.

[GlenM]

BTW,Doc. You were right I do like this diagonal.

 

Glen.