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Old 27-01-2019, 10:34 PM
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FredinBroome (Fred)
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Tele Vue 2X Barlow Vs Powermate 2.5X

Hi everyone,


I have heard it suggested that dobsonians and perhaps my Meade LX200 will benefit best from a good quality Barlow 2X. I came across the Tele vue 2X Barlow and also the Tele Vue Powermate 2.5X and was wandering if there is a noticeable difference between the two apart from the 0.5X increment and the considerable price difference.


Interested to hear your input.


Cheers,
Fred
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Old 28-01-2019, 01:16 PM
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NorthernLight (Max)
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I have a Celestron 2x Barlow and 2.5 Powermate. The Powermate does not shift the focus point outward as the Barlow does and it has much better colour rendition. But I think the TV Barlow’s have good colour correction as well. The Powermate accepts a T-Ring and you can buy a camera bayonet Mount for it. The parts are sold separately but it is easy to mount a DSLR to a power mate and there are no backfocus issues. This was my main reason to get one. However, on my f/5 Newton the exposures required went up to something crazy like 15min. for the pinwheel galaxy as the system becomes f/12.5.
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Old 28-01-2019, 01:37 PM
Startrek (Martin)
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Iíve used both Barlow and powermates for visual in my 12Ē dob and without question the powermates are far superior especially for lunar , planetary and DSO observations. Clean crisp views with good detail to edge of field and no glare or stray reflection. I do use Televue Panoptic, Delos and Ethos eye pieces though , so what else do you expect !!
As far as imaging goes my powermates ( the full set 2x , 2.5x, 4x and 5x with T ring adapters) are excellent for lunar and planetary imaging with my DSLR at 5x magnification using BYEOS and stacking in Autostakkert 3. My f6 newt and DSLR combo has a sweet spot around F24 when imaging the planets
Yes they are a big financial investment but you pay for quality and performance and thatís exactly what you get
My 2 cents .......
Cheers
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Old 28-01-2019, 01:59 PM
astro744
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See http://www.televue.com/engine/TV3b_p...d=53&Tab=_back for an explanation of the difference.

Visually the Powermate allows the eyepiece to perform as designed with no shift in exit pupil and therefore no vignetting. They are heavy though in the 2" sizes but do give excellent results. One of the best views of Saturn I ever had was with a 35mm Panoptic and 4x Powermate (10.1" f6.4 Newtonian) but I did need a counterbalance even at high altitude as the weight was too much.

The 2.5x Powermate was redesigned I believe as the original would not take filters. Bintel still show the original on their web site but Tele Vue show the newer type. I cannot confirm that the new one is threaded but I see no other reason to change the barrel. I have the old one. See https://www.bintel.com.au/product/te...v=6cc98ba2045f

The Tele Vue Barlow is excellent though. If you plan on using with eyepieces that alresdy have a long eye relief such as 32mm and 40mm Plossl then the Barlow is not the best choice as it will throw that eye relief out further and for such eyepieces either a 2.5x (1.25") or 2x (2") Powermate is recommended. The 2" Powermate comes with a 2"-1.25" adapter.
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Old 29-01-2019, 06:30 PM
TareqPhoto (Tareq)
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I have Powermate 2X, but i am planning to get 4X and 5X too for imaging, i do have Tele Vue 3X Barlow, but as they said, Powermate is higher performance than standard or non Powermate ones, it is just i don't know how good quality is for 4X and 5X if using for imaging only, i thought that going higher in magnification will degrade the quality either visual or imaging, or Powermate all of them are excellent quality no matter what magnification?


Also, i was thinking to complete the set, i have 2X and later i will add 4X and 5X, but should i get 2.5X too? i have F5 Newtonian, and later if things are right i may buy a Dobsonian too [F4.2 up to F5 option], my 7" Mak already has F15 so even using 2X it will give F30, then i don't know which camera to resolve that for planets, wish if TeleVue has kind of Powermate or Barlow at about 1.2X up to 1.5X for those slow scopes.
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Old 29-01-2019, 07:42 PM
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FredinBroome (Fred)
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Thanks everyone for all your insights. I think that the Tele Vue Powermate is definitely the way to go and in my case I will get the X2.5 so as not to duplicate my current lens sizes. My favourite lens is a Baader Hyperion Universal Zoom Mark IV, 8-24mm eyepiece 1.25" and the barlow from baader that suits this lens is a X2.5. That then will be my multiplier. Now to save my pennies heheh


Cheers, Fred
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Old 29-01-2019, 09:16 PM
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Stonius (Markus)
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It's worth mentioning that the backfocus of the imaging train should be taken into account when looking at the magnification specs, both TV barlows and powermates will change magnification the further you sensor is from the flange.

By way of example, at 55mm backspacing, a 4x Powermate and a 3x barlow both deliver 4.2x.

They have a little graph on their site that explains this, but it's only a factor for imaging.

Markus
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