televue powermate 5x

Hi,

Anyone have one of these? Basically its a 5x barlow, it seems to have a fairly good reputation.

I'm thinking of getting one as my scope isnt very good a magnifying things, in particular with a webcam (focal lenth is just over 1 meter). I have a Meade 2x barlow, and have used the meade 3x short barlow. Trying to get a decent sized Mars on the webcam ccd is the motivation behind this!

It works out at about 200EUR from the states/canada.

Any thoughts?

Cheers,
~Al (who really should start saving money and stop buying gizmos!)

I'm sort of in a similar situation myself Albert. I've just ordered a 2x barlow which hopefully will be useful to attach my webcam onto. I've an 8" f10 scope so by design it's capable of reasonably high magification. However, at 5x i'm just wondering just how good the image quality will be. It might not be of much use for putting eyepieces into unless you use it with a long focal length eyepiece and even then i can't see how it would compare favourably with a similar short focal length eyepiece even if it is televue. This would imply that it will only be useful for the webcam. Have you removed the lens from the webcam and pointed it at the moon through the scope? How much of the moon can you see approx? This would give you an idea of the camera's field of view. Dividing this by 5 would presumably give you the field of the view of the webcam with barlow and hence a magnification. Is this magnification achievable with your scope on a typical night is a question you will have to ask yourself depending on the size and f/ratio of your scope. Also, mars' disc would need to be within the range of approx 15 to 30% of the resultant field of view for it to be useful. If the apparent size of mars is too small, then it's no use. If the size of mars is large relative to the resultant field of view, it will be very difficult to get mars to appear on the webcam in the first instance and then keep it there steady. Does what i've just said make sense to you? I'd be interested in your or anyone else's feedback on this as i'm trying to understand it all myself. Some people just buy one good quality 2x barlow and another second hand one and stack them. The good quality one can be used with eyepieces also and i'm sure the total cost would be well under 200 notes. How good is the image quality, I don't know. Alternatively you could attach the webcam onto your eyepiece with/without webcam lens. Haven't tried this myself yet but would be interested to know how well this works. Hope this provided some food for thought. Keep us informed as to how you get on.

Hi,

I can see roughly www.cademuir.net/astro/images/moon.jpg that much of the moon in the webcam, I'll have to work out exactly how many arcsecs that would be with a 5x tonight.

I've tried stacking the 2x barlow with a 3x meade `shorty` barlow, I wasnt that impressed with the resultant image. Not sure of the corect optical term, but there was noticable red fringes on the top of the pbjects and blue on the bottom. This was possibly due to things being slightly out of alignment as the weight of the barlows and the wecam could have pulled them out of line, or possibly there was just too much glass.

Once I can keep the image reasonably steady (i.e. stay in the frame!) then I'll be happy enough, the software can sort it out! The scope is a lot more steady now that I've removed the teflon washers from the mount.

I've never tied to attach the webcam to an eyepiece, all just prime focus stuff so far. I'll give i a go some night when the boss gets back and I can borrow his laptop!

Definatly more for me to think about anyway.

Thanks,
~Al

As the moon is approx 30 arcmin wide and you have approx 1/3 the width of it there in the image, then the 5x would show up about 2 arcmins - is this a reasonable assumption? Mars at 26 arcsecs would then take up approx 1/5 of the field of view ie. approx 20% of the webcam's FOV with the 5x barlow. This doesn't seem too bad actually. Oh and as for stacking the barlows, I thought you might get that colourful effect -(is that what they call chromatic aberration?). Same reason I think people are slow to attach the webcam to the eyepiece - although don't let this stop you from trying. Check these figures again and see if they make sense.
Michael

Hi All,
I managed to get my hands on a Toucam pro (Michaels recommendation) and I discovered one very nifty thing about it.

If you leave the lens on the camera and use an eyepiece (say 26 mm), you effectively have a varialbe zoom lens camera. By unscrewing the webcam lens as far as possible (without it coming off), you get a fairly wide field of view, nearly half the field of view of the eyepiece, if you screw the lens in as far as possible, you get a very narrow field of view (around three times zoom as far as I remember). I used elastic bands to attach the camera to the eyepiece, not the best but its fairly stable.

BTW, You focus the camera by twisting the Lens, so the lens can pop out, great I though so now I can do high mag imaging through the scope also.

Hope this is helpfull.

If you seeing red on the one half of an image and blue on the other half, the camera is probabily not square to the mirror/lens of your scope.
Is the colour full red on one side of the focus and blue on the other ??
If soo this is probabily the cause, otherwise you might have some type of chromatic abberation or lens defect.