Powermates or Barlow?

Markaus · #1 11-06-2011, 05:29 PM

Any suggestions on what would be better? If theres a link to a previous post please let me know.

Im looking to use it with my Webcam to bring the detail out in the planet and photos

Also it would be used with my normal EP for general enjoyment

asimov (John) · #2 11-06-2011, 05:41 PM

The only barlow I've owned & use regularly is an 7 year old Meade APO 2X & so I can't really comment on latest model(s) barlows.

I own 2 Powermates as well, & can't fault them, so I'd probably reccomend a Powermate.

renormalised (Carl) · #3 11-06-2011, 05:52 PM

Powermate...wins hands down over normal barlows, although a good apo barlow will make a good addition to your equipment. What scope are you planning on using with the powermate/barlow/webcam combo with??

Markaus · #4 11-06-2011, 06:23 PM

Hi Carl, will be used on my LX90ACF 8"

So, looks like a Powermate then. is the 2.5x the max for the Tele Vue Powermate?

Possibly keep an eye out for a Barlow as well...

renormalised (Carl) · #5 11-06-2011, 06:44 PM

Same scope as I have....grab the X5 Powermate. You can get upto x7.7 of the FL depending on how far away from the focal plane of the camera's chip you set the lenses in the powermate. However, to be practicable with an 8" scope, I wouldn't push it anymore than x2-x4 for normal nights. That'll still give you an effective F ratio of F20-40, which will really make any planet look good

Goto Bintel and have a look in their eyepieces section. That's where you'll find them.

Markaus · #6 11-06-2011, 06:58 PM

Carl cheers

Just a question as im still learning..... You said get a x5 which is fine.. But then you mentioned you wouldnt push it more than a x2 or x4, does that mean i need to buy 3 powermates?

Thks

renormalised (Carl) · #7 11-06-2011, 07:14 PM

Quote:

Originally Posted by Markaus

Carl cheers

Just a question as im still learning..... You said get a x5 which is fine.. But then you mentioned you wouldnt push it more than a x2 or x4, does that mean i need to buy 3 powermates?

Thks

No, not unless you want to

A x2.5 and x5 Powermate would be more than sufficient

Use the x2.5 for visual stuff and the x5 for piccies.

The only time I will push a x5 powermate to the max is on really steady seeing and good transparency, otherwise your views will tend to be wonky because of the atmospheric conditions.

It's the same with barlows. To really get the best out of them, especially high powered ones, you need steady seeing and good, clear sky. Same with eyepieces too. You just have to judge the conditions and make your decisions based on what you think you can do.

Also, there is a trade off with getting these long FL's. The longer the FL you use, the smaller the FoV and the dimmer the image. Sometimes, bumping your F ratio up to crazy numbers like F50, F60 or F80 (which can be done with a x5 powermate) is just impractical, even on really great nights, just because the object you're looking at is so dim it's even no good through a CCD/webcam. You can compensate for that with larger aperture (more light gathering capacity), but you have to work with what you've got.

Rigel003 (Graeme) · #8 11-06-2011, 07:33 PM

Most SCT users doing webcam planetary work will use a 2x or 2.5x barlow or powermate, taking your effective focal ratio to f/20 or f/25, which is pretty much ideal. With 5x your light drop off will require a glacially slow frame rate, longer exposures that won't freeze the seeing well, or a very much underexposed histogram. The 2.5x powermate works well but this particular powermate has an unusual characteristic you need to watch out for. All barlows and most powermates will have an increased image scale (beyond the 2x) if you insert extra space between the barlow and the webcam with an extension tube. However the 2.5x powermate actually has a decreasing image scale with further distance. Somewhere on the Televue website there's a graph of the effective magnifying power of each with increasing distance.

renormalised (Carl) · #9 11-06-2011, 08:58 PM

As Graeme just said, that's the unusual thing about the x2.5 powermate. You can see the graph at Bintel when you click on the further info link on the powermate page.

The best use for the x5 powermate is with CCD imaging. There you can use a CCD camera's ability to take long exposures to get the light onto the chip. But, as I said earlier, the bigger your aperture, the more light you'll gather, the brighter the image (to a certain extent...you can bump up the FL too far even for a big aperture).

renormalised (Carl) · #10 11-06-2011, 09:15 PM

If you want to see what insane FL does to planets with an LX90, goto the Meade LX90 Photo Gallery and have a look. Remember, the pics have been processed.

Markaus · #11 11-06-2011, 09:30 PM

wow!

Im currently hunting ebay to see if there are any deals on powermates and barlows...

renormalised (Carl) · #12 11-06-2011, 09:33 PM

What's even more interesting is that the guy who took those pics was using an 8" LX90.