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To support my future dream telescope system, I'm going to need a 2" diagonal for low-power visual use, with 35-55mm eyepieces.
This will be for a slow catadioptric (f/10 or slower) telescope. Example: Vixen VMC260L (f/11.5).
Does anyone here happen to have experience with, and/or a willingness to comment on, the Altair 2" Positive Lock 90 Degree Prism Diagonal?
I'm rather impressed by this advertised claim: "The prism surface cannot even be seen with the naked eye when looking into the diagonal, unless there is dust on the surface."
Thanks!
* Meade 323 refractor on a manual equatorial mount.
* Celestron C6 SCT on a Twilight 1 Alt-Az mount
Prof. Barnhardt to Klaatu in The Day the Earth Stood Still: "There are several thousand questions I'd like to ask you.”
Looks like a well made diagonal at an attractive price. I don't have hands on experience with this brand, but prisms in general work nicely in catadioptrics.
I don't have experience with this but I have bought a few Altair products. Why not send an e.mail to Nick he'll tell it to you the way it is and he's a partner in Altair. Their backup and customer service is the best.
Thank you all! I have been persuaded enough to actually order one (even though I haven't yet purchased the telescope with which I will ultimately use it!)
* Meade 323 refractor on a manual equatorial mount.
* Celestron C6 SCT on a Twilight 1 Alt-Az mount
Prof. Barnhardt to Klaatu in The Day the Earth Stood Still: "There are several thousand questions I'd like to ask you.”
When looking at using a prism diagonal you first need to check your telescope too see if it may benefit from using one.
Do a star test and on the in-focus view see if the first airy disk has a red ting to it.
If it does your telescope may benefit from using a prism.
If the disk is white/ neutral in colour then a prism may not be a benefit but actually detract from the views.
Typically longer focal length telescopes should have no issues using a prism and shorter f/8 and faster will benefit from a mirror.
This is not always the case though so you must test first to know for sure.
This applies for achromatic as well as apochromats as some fast apochromats have no issues using a prism and some slow achromatic show no benefit either.
Some prisms such as the Baader 2" Amici prism: https://www.baader-planetarium.com/en/a ... ating.html work exceptionally well with some apochromats when doing high power planetary/ lunar viewing as well as with the brighter DSOs.
The other thing to keep in mind is that though something may look similar between different vendors it does not tell you the level of QC that has been performed on it.
I have not used the Altair prism so cannot directly comment on it though they do have a good reputation for quality so I would expect it to be good.
APM I have used before and their QC is excellent and they maintain a high standard, Teleskop-Service is another retailer that maintains a high standard as well.
Picking astronomy gear simply by what it appears to look like would be the same as buying your next vehicle while standing a kilometer away and choosing by what colour it is.
Gabrielle See Far Sticks: Elita 103/1575, AOM FLT 105/1000, Bresser 127/1200 BV, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS 100/1000, Vixen SD115s/885 EQ: TAL MT-1, Vixen SXP, SXP2, AXJ, AXD Az/Alt: AYO Digi II, Stellarvue M2C, Argo Navis encoders on both Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102 Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Tak prism, TAL, Vixen Eyepieces: Antares to Zeiss (1011110) The only culture I have is from yogurt
I hear you Gabby. However, now days so many products (not just for Astronomy) made on one factory in China and sold under many brands.
I also realize that vendors can request different finishes for their products, but for relatively small vendors like APM and Altair it would make perfect economical sense to order small batches from the same production run.
This thread inspired me to purchase Altair 2" prism to. It was delivered to California from GB in less than a week and cost ~$178 with shipping. Good deal for a quality 2" prism.
I will agree to a certain point but a lot of retailers here (Altair, APM, Baader, Bresser, TS, TeleVue, Oberwerk to name just a few) actually have their own QC or independent QC inspectors in these factories looking over their orders to make sure the minimum quality is met and maintained.
We of course pay for that quality in slightly higher prices and have to trust that they are not just pulled off of the production line that was in the middle of doing an order for average retailer X.
I think the major difference is a retailer that orders an allotment for sale at their shop compared to a retailer that has their own brand that is expected to maintain a certain level of quality.
Gabrielle See Far Sticks: Elita 103/1575, AOM FLT 105/1000, Bresser 127/1200 BV, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS 100/1000, Vixen SD115s/885 EQ: TAL MT-1, Vixen SXP, SXP2, AXJ, AXD Az/Alt: AYO Digi II, Stellarvue M2C, Argo Navis encoders on both Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102 Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Tak prism, TAL, Vixen Eyepieces: Antares to Zeiss (1011110) The only culture I have is from yogurt
