Saturn is coming - Barlow or what?

[Kaptain Klevtsov]

Been looking at the Hyperion eyepieces which can be fitted with a T ring to fit a camera on top of the EP. Would this work better than a Barlow lens for Toucamming planets, or would I be better off spending my pennies on a high quality Barlow lens?

Which is the better way to skin the cat?

Captain Chaos

[FLO]

I am no expert but I would have thought something like this would be better:

http://www.firstlightoptics.com/proddetail.php?prod=ae4ximagemate

[GordonCopestake]

You want to be at about f/20 so unless you have a long focal length CAT you need to barlow (or powermate)

[russ]

Can't beat a barlow for planetary imaging. Although personally I would not want to own the AE 4x Imagemate again (apologies Steve :?). A poor barlow by comparison to others available for the same money. The TAL 3x is a better bet and available from Steve. Better still is a Televue 3x barlow secondhand (plugging my own item i need to sell ). Although these are for faster scopes (f5 - f8).

An f10 SCT or f13+ MCT will only want a 2x barlow (Ultima or Shorty Plus) or a TeleVue 2.5x Powermate (beautiful).

Russ

[FLO]

I would not want to own the AE 4x Imagemate again (apologies Steve :?)

I did say that I wasn't an expert.

Odd though, because its a good seller and pre-owned ones are quickly snapped up.

What is the alternative, for the same money, that you recommend?

[Chubster]

Better still is a Televue 3x barlow secondhand (plugging my own item i need to sell smiley). Although these are for faster scopes (f5 - f8).

Didnt know certain barlows were better for certain fnumber scopes ? I have a meade 2x shorty barlow and I am looking to tentatively start imaging, will this be OK for me? Also am I correct in saying that if, like me you have a f5 scope a 2x barlow then makes it f10 so to get it to f20 would require a x4 barlow

chubster

[russ]

Perhaps I had a duffer Steve? At the time (2004) it was the only affordable 4x option for a Newt. But now there are plenty of good quality 3x barlows available and also a 5x barlow from Antares which has had some good reviews.

I found my Imagemate to poorly be corrected for colour and pretty soft. But it could have been a lemon.

Chubster, I found with my Explorer 200 the Antares 3x, TV 3x and 5x Powermate all worked well. Image scale was a little on the small side with a 2x barlow.

Russ

[GordonCopestake]

Chubster, if you can afford a 5x powermate you'll love it. A fantastic "barlow". Be warned though at those high f/ratios you will have difficulty keeping your target in your FOV

[Chubster]

God...you guys are costing me a fortune PM Steve ??

[GordonCopestake]

It's an expensive downward spiral. I stopped attempting to image when i made this image a while ago. This setup is considered a cheap one and i still hadn't got everything i need or have a particularly impressive rig

I dont own a single piece of this any more strangly. Wish i did actually looking at it hehe

[Chubster]

cool setup though ! Love the size of the "finderscope"...hmm thats got me thinking perhaps I could attach a 6" Newt to mine

[Kaptain Klevtsov]

So the answer is go for the Barlow. Thanks for the responses guys.

BTW I don't get the "you need f/30 for planets" thing. I could use the f/5 Newt. with the lid on and just remove the small cover, that would give me a very high f/ ratio but not do the job properly, surely I just need enough focal length? Again, using that way of thinking, I'd be better using the f/8 frac. over the f/5 Newt. which have the same image scale, but I get more light through the Newt.

I expect big Dobs. like Arthur has would give a wicked view of the planets close up but with a fast f/ ratio. Be a fun thing to keep aimed though.

Sounds like russ could be getting a PM soon when the bank goes black again.

Captain Chaos

[Chubster]

:) Your doing it on purpose im sure.

I could use the f/5 Newt. with the lid on and just remove the small cover, that would give me a very high f/ ratio

can you tell me how this works and when you would use it cos im confused now what with fnumber, barlows, ratios.......

Chubster

[russ]

I could use the f/5 Newt. with the lid on and just remove the small cover, that would give me a very high f/ ratio

can you tell me how this works and when you would use it cos im confused now what with fnumber, barlows, ratios.......

that's true, stooping down the aperture will boost the focal ratio but not the focal length. And thus not the image scale. All you'll end up with is a 60mm f20 or something.......useless! It's focal length that gives image scale, not the focal ratio.

If you have an 8" f5 (1000mm focal length) Newtonian, you'll be looking to boost it too f20 or 4000mm focal length by using a 4x barlow (4 x 1000mm).

But if you have a 8" SCT working at f10 (2000mm), you'll still be looking for f20 (4000mm) again but will only need a 2x barlow.

Stopping down the aperture is only useful on the Sun and Moon. Definitely not for the planets.....need all the aperture, resolving power and light gathering you can get.

Regards

Russ

[FLO]

An f10 telescope means simply that its focal length is 10x longer than its aperture. If CC reduces the aperture, he increases the f-ratio.

1000mm focal length / 100mm aperture = f10

1000mm focal length / 50mm aperture = f20

and so-on.

[FLO]

Sorry, Russ beat me to it (the 'someone has previously posted' warning doesn't always work!)

[russ]

And not a good move.

[russ]

Sorry Steve didn't mean to steal your thunder. However yours is far easier to read, so it was worth the effort

[GazOC]

IMHO it's easier just to forget about focal ratio when you are starting out. As Russ and Steve have said focal length gives image scale and aperture gives resolving power, thats all you really need to remember.

You can always derive focal ratio from those two if need be. If somebody posts an image using a 200mm SCT at f20, just figure out the focal length to get the image scale rather than worry about the f#.