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Mamba
26-10-2017, 09:20 PM
I have a TSA 120 and a Televue x2 powermate which effectively gives me an f15 telescope. With this combination l am able to use binoviewers without the need for a corrector.
For some unconscionable reason I have convinced myself that I would be better off with the Tak 1.5 extender in place of the TV powermate for next years' planetary fest.
The extender costs $540, an addional planetary scope, say, a 100dl costs $3600, don't quote me as it's late but you get the idea.
Is there anyone out there who would be brave enough to offer an opinion on an extender against the powermate.
I would hope to use the extender with the binos but it would not a deal breaker if this was not the case.
I have already ordered the extender from Claude once before and then cancelled it, I don't want to mess the guy again as he comes across as a bit of a gent.
Dave Cooke

Kunama
27-10-2017, 05:40 AM
Dave I think it comes down to ergonomics, the extender means that your binoviewers will sit lower down rather than on top of the TV PM.

Using the extender will also allow you to binoview without a GPC in the light path. I guess it also depends on the eyepiece pairs you have and what magnification you get when using the 2x or 1.5x.

If you go with the extender you still have the option to include a GPC1.25x in the mix, which gives you an effective focal length of 1687mm.

The GPC not only gives a reduced need back focus but also corrects for the SA introduced by the prisms of the binoviewer.

As nice as the DL is, the additional aperture of the TSA120 will allow you to see more detail than the 4" scopes.

If you're after more from the planetary fest of 2018 maybe a used Mewlon210 :D:D

Atmos
27-10-2017, 06:44 AM
Maybe the GPC 2.7x would be better? As Matt mentions, the extender is ergonomically less convenient. The 2.7x gives greater magnification than the TV2x Powermate and as Matt also mentions, it corrects for SA.

Mamba
27-10-2017, 11:23 AM
Having given denis 008 a bucket load of loot for a pair of his Zeiss binos which have 30mm of clear appature I have been reluctant to use a corrector of only 24.5mm diameter with the resulting loss of light.
I am able to come to focus without a corrector with the following set up.
TSA120 - Tak 3inch extension tube - TV X2 powermate - Baader T2 prism - Zeiss binos - 2 Baader 8/24 Mk IV zoom eyepieces. This setup means that I do not have 1.5kg of binos and eyepieces balanced on top of a powermate which itself is perched on a diagonal, the drawback is that with the powermate being so far removed from the eyepieces the magnification is huge, I estimate X4 although I admit that I don't know how to work it out mathematically.
I am thinking/hoping that the Tak 1.5 extender could replace the powermate and then give me a more standard magnification.
eg, 900x1.5 devided by 8 = 169 whereas at present I estimate that the 8mm eyepiece is giving me something of the order of 450! while the minimum mag is around 150. I know the Tak is good, but that good?
Sorry about the upside down photo, cannot seem to correct it on my iPad.

Atmos
27-10-2017, 11:45 AM
With your current eye pieces you have nothing to worry about with the clear aperture of the GPC. It might be smaller than the 30mm clear aperture of the Bono’s but that’s only useful if you want to do lower power viewing with maybe 24mm panoptics where you don’t want the extra magnification anyway.

Kunama
27-10-2017, 01:56 PM
That setup is indeed very high mag, the PMx2 working more like 4x.
You might be better off with the EX1.5ED. I use Tak Abbe and LE for planets ranging from 5mm to 32mm.

I turned your pic the right way up for you....

Merlin66
27-10-2017, 03:29 PM
David,
""
the drawback is that with the powermate being so far removed from the eyepieces the magnification is huge, I estimate X4 although I admit that I don't know how to work it out mathematically"

Hmmm, this is not the case with the Powermates (with conventional barlows yes ) the magnification is almost constant with any spacing - it will be very close to x2.

See: http://www.televue.com/engine/TV3b_page.asp?id=53&Tab=_app

Kunama
27-10-2017, 03:47 PM
That's interesting Ken, with a distance of 200mm from top of PM looks like it might be around 2.3x.

Merlin66
27-10-2017, 03:52 PM
I use my PM's with the T thread adaptor which gives a solid connection and also significantly reduces the length and overhang....

Mamba
27-10-2017, 05:05 PM
Ken,
Thank you very much for the info regarding the TV powermate. I am only just setting this system up and my first feelings were "Thank God I can achieve focus" and then "The Moon looks big"
As Matt says if the distance is about 200mm then an 8mm eyepiece would yield about x259 (900x2.3 divided by 8) which would be ideal for this size and class of telescope, I could not ask for more really.
I like the idea of the T ring adaptor for the PMate, unfortunately they are not listed on Bintel's website so I shall give them a call tomorrow. Anything that provides a more substantial means of attaching such expensive equipment is to be welcomed.
I will post the results when I have fitted the T ring adaptor as there is not a lot of information out there as to what will work and what will almost work.
Dave Cooke

Merlin66
27-10-2017, 05:11 PM
I donít know about your set-up but the T2 (and a T tilter) works for my solar imaging.

AstroApprentice
27-10-2017, 06:08 PM
PM T2 adapters under imaging accessories. ideally should be a link from PM pages
https://www.bintel.com.au/product-category/imaging/imaging-accessories/page/2/

[QUOTE=Mamba;1342086]
I like the idea of the T ring adaptor for the PMate, unfortunately they are not listed on Bintel's website so I shall give them a call tomorrow.

Mamba
27-10-2017, 06:33 PM
Thanks Jason,
I must confess that I didn't look at the imaging items.
Will be ordered tomorrow.
Am outside at present, for the first time in days it is clear but hazy but good enough for the Moon.
With my setup as described with the eyepieces set at 24mm I cannot quite see the full disc, or I couldn't if the full disc were there. If the moon spans 30 mins I can probably see 28/29 mins.
Once again Thanks for the tip
Dave Cooke

Mamba
28-10-2017, 05:50 PM
Following my previous post of last night and determining that I was seeing a TFOV of 28/29 arc minutes I utilised the Naperville Astronomical Association's telescope calculator. Baader state that their zoom eyepiece will provide a FOV of 45 degrees and feeding this into the calculator reveals that I was getting a magnification of somewhere around 276 to 288, and that the 2xPowermate was providing 2.44 to 2.55 times. A little short of my claimed x4.
I am indebted to Ken and will reflect on the error of my ways, grovel, grovel.
But seriously moon the did look big.
A Powermate T ring adaptor is on it's way.
Dave Cooke:ashamed::ashamed:

Merlin66
28-10-2017, 07:36 PM
David,
Don't worry about it...
I've been practising astronomy for 50 years and still get it wrong!!!