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Can flextube 250 auto tracking handle 4-5x barlow?

Space Cowboy

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Moonshane

Moonshane

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not sure why no-one has replied to this. the problem is not whether the scope can handle the barlow it's whether the scope/seeing can handle the magnification. also a barlow generally increases the eye relief of the eyepiece so a 5x barlow would increase an eyepiece with 20mm ER to an eyepiece with 100mm ER (I think). seeing in the UK for visual is often limited to 150x-250x. in your scope (assuming it's a 1200mm focal length) this would mean an 8mm or a 5mm eyepiece. therefore I don't see a 4-5x barlow being much use for visual, possibly in ANY scope.

are you thinking of imaging with eg a webcam? if this is your 'angle' then I think the broad answer is 'yes' but I'd suggest a Televue Powermate would suit you better. This is optically better than any barlows I have tried and leaves the ERof the EP and focal length of the scope the same but magnifies the image by the factor of the Powermate (1.25" come in 2.5x and 5x and 2" in 2x and 4x).

I hope this answers your question? I am not an imager but answering on the basis of the comments of others.

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NickH

NickH

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Yes, it can easily..if you have good tracking/well set up..

It takes it to F25, and will deliver nice views of planets and the moon..

I am outside right now with a TV2.5X powermate on a 12" Goto dob eyeballing the Moon..

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Moonshane

Moonshane

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ahh, sorry I misunderstood.

I think the problem with eg a 5x barlow on the 250 is that to get say a 5mm equivalent, you'd need a 25mm eyepiece. assuming 20mm ER, and assuming I am correct about the 5x factor on this then you'd be a fair way off comfort in viewing, if you are 80mm off the eyepiece. would be useful if someone can confirm that my assumptions are correct on this. this is why I recommended the Powermates such as the one you have (or just straight eyepieces, which is the way I went after I sold mine).

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Space Cowboy

Space Cowboy

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Thanks for your replys guys!

Sorry Shane I should have stated imaging with a webcam. My skymax 127 has focal length of 1500mm and I'm imaging at 3x Barlow plus the webcam chip which i believe is equivalent of 5 or 6mm eyepiece so we are talking about roughly 900x maginification. The 250 flextube is 1200mm focal length so to achieve the same magnification it would need at least 4x Barlow. Obviously i would not be trying to observe at these magnifications but i have taken note of your powermate info :-)

Nick do you think the flextube can track a Planet for 2 or 3 mins at 900x plus?

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NickH

NickH

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yeah...same here mate, seeing as how it can't find Jupiter at the mo, this should be amusing! (bug in software). I have done some lunar runs on it so far, and it held well...but Jupiter not yet..mainly as I don't want to even attempt to post any Jupiter images after seeing Neil/Pete/Damians :-)..

Hits DSO's bang on the money

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NickH

NickH

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Okay...so far tonight it's held Vega within a smidge of the centre of a 16mm EP for 2 hours and 42 minutes tonight (8pm to 10:42 when I last looked)

About to put it on Jupiter with a 5mm EP.. I have no doubt at all it will hokld it for >20 minutes

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NickH

NickH

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Okay the seeing/clouds are pants... but I put a 9mm illuminated rec on the 2.5X powermate, and stacked that with a 2X barlow.. giving around a 2mm EP...just to test the tracking...not the optics, etc

Held for 28 minutes in that FOV... it was fully inside the cross of the rec for over 7, and the drift seemed to be due to the slope it is on...I know it's not dead level. Marginal backlash when you centre it up..and I mean marginal, at that mag, jupiter moved around 1/2 it's own width back when I let go of the hbx buttons

Then put on a 4X AE imagemate, and re centred, and again over 20 mins so far...

Yes, it's pucker...

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Space Cowboy

Space Cowboy

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Okay the seeing/clouds are pants... but I put a 9mm illuminated rec on the 2.5X powermate, and stacked that with a 2X barlow.. giving around a 2mm EP...just to test the tracking...not the optics, etc

Held for 28 minutes in that FOV... it was fully inside the cross of the rec for over 7, and the drift seemed to be due to the slope it is on...I know it's not dead level. Marginal backlash when you centre it up..and I mean marginal, at that mag, jupiter moved around 1/2 it's own width back when I let go of the hbx buttons

Then put on a 4X AE imagemate, and re centred, and again over 20 mins so far...

Yes, it's pucker...

Great work Nick! You've answered my question with flying colours! Sounds like it tracks a lot better than my skymax GOTO mount...I was fighting to keep Jupiter in view with a 4x barlow last night lol I would imagine the low centre of gravity that the Dob mount has is ideal for stability. Just a slight breeze makes this skymax mount's tracking go off kilter.

Many thanks!

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Space Cowboy

Space Cowboy

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fairly old thread from sep last year

but colour rgb Jupiter pic at bottom of page looks very good,

albeit he was using dmk rather than webcam

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3265288/page/0/view/collapsed/sb/5/o/all/fpart/2/vc/1

James that image is very good! You've got me salivating now lol :)

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