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.

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.

Have a look at www.cademuir.net/astro/images/saturn.jpg see the way the top is blue and the bottom is orange? Its a stacked webcam image, though a single frame shows the prooblem also www.cademuir.net/astro/images/saturn-single.jpg

It keeps the same orientation when I rotate the webcam which would suggest something with the scopes optics, though I cant detect this visually.

Cheers,
~Al

Was it taken with the camera lens in or out?
Was it taken using an eyepiece or just the barlow?
Michael

Sorry I should make things clear when I post!

Was it taken with the camera lens in or out?

This was with the lens out. The lens of the toucam unscrews exposing the ccd. I have an adaptor that screws into the camera and lets me slot it into the focuser.

Was it taken using an eyepiece or just the barlow?

Just the barlow, I'm not using any eyepieces in this method.

Cheers,
~Al

To be honest Albert, I'm flummoxed!
If you had told me you tookthe image any other way, I'd have said it was due to all the glass. However, you have minimised it as much as possible. I can't see how the problem would be with the barlow. We all know the reputation TeleVue have. And it's an LXD55 you have, if memory serves me correctly, which is reputed to have good quality optics. The Mogg adaptor also ensures that the CCD chip is perpendicular to the light path.
Did you try stacking the image with Registax 2. I don't know much about it but I think the new version can help correct for chromatic aberration. Might be worth looking into.
I also think I remember reading somewhere that some people remove the little piece of glass that is on the CCD chip itself. Don't know how accurate this is or if I have my story mixed up. Look it up though - may be useful.
If worst comes to worst, at least you'll have very good quality B/W images. Don't know how much consolation this is to you though.
Anyway, food for thought - hope this is useful. Keep us informed. I'd be interested if you can progress any of these issues.
Michael

Thanks I might try taking the cover off the CCD, but I cant imagine it being responsible for such a dramatic effect.

One point, Im using a Meade APO 2x barlow not a televue (yet! cause they are out of stock, and changing the powermate 5x to have a tring adaptor on the end, hence the shipping delays)

There are a couple of experiments I can try next time its clear:

1. Rotate the webcan in the focuser to be sure its not part of the webcam.
2. Rotate the optical tube of the scope and see if it keeps the same orientation.

This should rule out or pinpoint any scope problems. One suggestion I got on the lxd55 list was that it could be atmospheric diffraction (refraction?).

I've got registax 2 though I cant see where it is doing colour alignment, does it split the avi file into 3 (red green blue) align, stack, then merege them? There are some LRGB controls but not the functionality im looking for I dont think. is there another tool that I can use to split the avi into colour streams first?

Cheers,
~Al

Just check with others about my hunch about removing the cover of the CCD - just in case! I have to agree though, I can't see how it would be responsible. Reg 2 can do "chromatic shift" I think it's called. From what I remember, it can move red or blue horizontally or vertically relative to the rest of the image. It consists of a little box that you tick on one of the main screens. Ticking the box opens up a new panel which gives you the relevant controls. Have a look at this link
aberrator.astronomy.net/registax/html/rgb_shift.html

Hope this is of help.
Michael

michael wrote:

Have a look at this link
aberrator.astronomy.net/registax/html/rgb_shift.html /quote]

So thats what that box does Thanks for the link I'll try that tonight.

Ive checked up on the CCD, and some folks do remove it but only as it blocks some wavelengths. It seems more for the perfectionists! I think I'll leave it there to protect the CCD chip for the moment.

Thanks,
~Al

By the way, you don't have an IR filter by any chance do you (not that I think this is at fault or would solve the problem). I've seen where some people swear by them, especially for imaging Mars...where do you get them or can you make your own??
Michael

One of the guys in the club (SAC) has a 2x meade barlow (the short focus barlow) and it work very well on his scope which is a ETX90 (90mm MAK F14).
I tried it out on my scope (12"SCT) and the chromatic abberation (colours) was severe, bad colours around stars, like coloured wearing 3D glasses. The reason for this is the the shorty barlow is designed for F14+ systems and when I put it in on my F10, its been pushed beyond its design spec.

I see that the LXD55 is a pretty fast scope so maybe the 2X apochromatic cant handle the fast scope given that most of Meades gear is F10+ (except for the LXD55s of course) and this barlow predates the LXD55 by years

ANOTHER POSSIBILITY, is atmospheric defraction. If the object is near the horizon (within 30degrees) you do get red/blue edges on objects. This is very noticable on bright objects like Venus and gave me a heart attack when I first saw it. See if the orientration changes through out the night.
Sorry for the long mail, hope its useful.

For Gods sake don't take off the protective screen from the CCD !!!
A spec of dust on the CCD will block image area, the damage you could cause cleaning it is irreversible, you're basically touching the surface of an integrated circuit !!! static electricity .. etc....
and atmospheric moisture will corrode it in a matter of months (depends on how good the surface coating on the chip is)!!!