Premium Barlow or Powermate ??

[Kai]

I am looking to do some long focal lenght imaging of Mars later this year as its meant to be nice and high.

Using th C8 @ F10 i already have a nice x2 Barlow.

The question is if i go for a 3x barlow bringing it to F30 what would be the better way to go ?

Either a Televue x3 barlow or a Powermate.

I will do some visual with it but the majority hopefully will be imaging.

[MartinB]

For the C8 I've found that F30 is pushing things a little too far. A x2.5 would be ideal. The powermate is a bit of a price though - £155 at Venturescope. WO do a 2" x2.5 apo barlow for £110. Again pricey but F25 is spot on for the C8 and toucam combo.

[themos]

I don't see a toucam in the list of equipment. Will the specs of the camera make a difference to the recommendation for the sweet spot f-number?

[Helen]

I was wondering the same thing Steve as I finally got the toucam working last night. Thanks for the advice Martin - its great to have advice from someone with the same set up. (Off to NY next week and was seeing a trip to Adorama coming on - WO barlow $155 )

Helen

[Kai]

Cheers Martin

Okay so at F25 is there that much more increase in image size as opposed to F20 ?? the jump from F10 to F20 is marked.

And given price isnt the issue (it is but i have to ask the question ) would YOU go for the Powermate or the Apo Barlow ??

Thermos

Sorry i didnt mention i was planning to use it with my Toucam

[SteveL]

...Off to NY next week...

Any room for a Milbiurn or APT wedge in your return baggage allowance? Its only 35-45lbs

[MartinB]

There is a formula for calculating the F ratio sweet spot for scope and camera and I just can't remember it or where I got it from. I posted it on SGL months ago but can't find it. I remember working out that for my set up C8 and toucam F25 was as far as you can go.

I really don't know about a barlow or a power mate. There are others on here who know more about this stuff.

[Kai]

Cheers Martin

Helpfull advice as always

Maybe its hidden in the vaults,I will ask Grant to have a dig for me