View Full Version here: : Is my 2.5x Powermate faulty?

28-09-2006, 08:04 AM
Hi guys,

As we all know, the skies lately have been less than impressive and so I have not had very many chances to try out my new XW's and Powermate. Anyway, I have now had a chance to try them several times and it has raised a question about the Powermate.

I have tried it on a number of occasions with the 7, 10 and 14 XW. The fields without it are clear, stars are sharp, sky is...well....about what you can expect in the 'burbs where you can read the printing on the eyepiece at 10pm without a torch. If I focus either side of centre, the stars turn to disks, nice and clear as expected. I put the Powermate in, and for want of a better word, the image "falls apart". I find it virtually impossible to get a sharp focus, the image goes from almost there with a little more movement in, to almost in focus with a little more movement out! In some cases, bright stars have the normal pair of spikes without it, put it in, and some of them scatter light everywhere. I cannot get a "clear" out of focus image of a bright star at all, the image is just bad. If I use the 2x Celestron Barlow from my eyepiece kit, I see the four spikes, a bit of chromatic aberation (not a high quality barlow) but the out of focus image is a nice clear circle, similar to when it is not there.

The other night I tried Jupiter. Without the Powermate, I could see the belts clearly in the 7 and 10. Put in the Powermate and I just can't focus it. I put in my old 2x Barlow, and the image was better.

Then I turned to the Moon, couple of days old. Nice sharp image. In the Powermate it is as if someone has been eating burgers and put their greasy fingers over the lenses, just slightly out of focus.

I have been checking the optics of the scope too to see if this is a possible cause, but that is another thread. But the fact that I can get quite clear stars, the diffraction rings are "almost" concentric (see other thread, but I haven't done that one yet!) seems to indicate that I should get a similar result with the Powermate in.

Am I missing something? The guff on the TeleView site implies that the Powermate should be suitable for any eyepiece and better than a Barlow.

28-09-2006, 08:14 AM
I think you could just be pushing the magnification too high, in bad seeing and on objects at low altitude.

The jetstream has overhead for ages now, and the bad seeing will mean that trying to go any higher than your 7mm on its own, is likely to produce very displeasing images that are blurry and difficult to focus.

The 2x may produce a slightly better image simply because it's less magnification.

I think you'd need to try it ONLY on your 14mm, which will you give the equivalent of a 5.6mm eyepiece, but again, ONLY when the seeing is good. It will be extremely rare that you'll ever use your 2.5x on the 10mm, and pretty much never on your 7mm.

It would be better to try the 2.5x on something around the 20/25mm focal length (equivalent of an 8/10mm EP), and hopefully you'd see a much better image .

28-09-2006, 08:28 AM
I actually thought of trying it with the 24 the other night, but that was AFTER I had brought it inside! I have also tried it on some stars closer to the zenith and the results are still less than expected. I will give the 14 and 24 a go next time the cloud clears...if I can remember.

28-09-2006, 08:29 AM
Hi one

I assume you are using the 8inch f5 scope where we are looking at a focal length of 1000mm. I suspect that you are pushing the mag too high and under poor conditions?

1000mm/7mm = x143. The x2.5 will give x357 which I think is too much and this will result in a very poor, soft image.

Even 1000mm/10mm = x100 plus the x2.5 PowerMate will give x250 and that too requires good seeing.

The Moon a couple of days old is low in the sky which generally results in poor seeing. Jupiter is also quite low and probably not the best candidate for testing the PowerMate.

It is not nice suspecting that your hard earned cash has gone on a poor quality purchase, so I feel for you. However, don’t give up hope just yet. Wait for a higher altitude Moon and better seeing and maybe use the 14mm then the 10mm to compare the results. Also, make sure your scope is well collimated as these "faster" scopes are more sensitive to mis-collimation.



28-09-2006, 08:29 AM
OoO, do you have any other eyepieces? How do they perform in the powermate?

28-09-2006, 09:25 AM
I agree with the others. I think you are just pushing the magnification too high in very poor seeing. Try using your 24mm Panoptic in the powermate and compare those views to the 10mm Pentax XW. Keeping in mind the Pentax will give a slighly cooler tone (whiter) and will have better light throughput.

CS-John B

28-09-2006, 12:59 PM
It was interesting that the other night, using the 2x Celestron Barlow resulted in MUCH less degradation to the image, even with the 7mm. As I recall, the 7 with the 2x looked better than the 10 with the 2.5x...although in both cases the image was pretty "soft".

The weather for the next few days looks promising so I will try some of the suggestions.

28-09-2006, 01:32 PM
Not many people are aware of this, but there is an electronic sensor inside Powermates that detects the presence of competitor's eyepiece and triggers passage of electrical microcurrent through a liquid crystal layer sandwiched between the upper two elements, effectively turning it into an extra refracting lens element, which was specifically designed to make it impossible to obtain clear focus. :P

Seriously, it sounds like you are pushing the power too high. Try with the 24mm. Like John says it will be a very warm image by comparison with the XW-10. My TV barlow warms the image through any EP, and I find the combo of TV barlows with TV EPs extra warm.

28-09-2006, 01:42 PM
I have an 8" f5 and rarely has the seeing been good enough to push the viewing beyond 200x (using the Vixen LVW 5mm).

I ended up selling my 3.5mm precisely because my scope couldn't support the extra magnification. You really need better than average conditions to push an 8" to 285x, IMO:)

The 24 in the 2.5x PowerMate will produce the equivalent of a 9.6mm eyepiece. You'd be better off using the 10mm native ..."un-powermated" and use the 24 for those nice wider views, also unbarlowed.

The guys are right. Back off the mag gas!!!!

28-09-2006, 01:45 PM
Have a look at this thread (http://cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/523562/page/0/view/collapsed/sb/5/o/all/fpart/1/vc/1) on CN for some food for thought. But do give the Powermate more of a chance, and in good seeing too. ;)

28-09-2006, 10:59 PM
.... sounds like I should stick my old Meade 140 2x Barlow, Fox.

29-09-2006, 11:29 AM
Nahhhhhhhhhhhhh !!!!

The TV Powermate is superb and a quantum leap ahead of the old Meade 140 which can "dim the image". It does an excellent job of being about as transparent as a barlow can be. It is also excellent in preserving the eye-relief of the native eyepiece, which is a big advantage with long eye-relief eyepieces like Pentax XW's, TV Radians or Vixen LV/LVW.

One of two things is going on here:-

Seeing is not good enough for the magnification or he got a dud powermate.

CS-John B

29-09-2006, 11:43 AM
:lol: John. Yes, you can certainly do a lot better than the Meade #140.

29-09-2006, 07:17 PM
... okay, okay, I have Barlow envy now...
It has crossed my mind to try out a 2.5 Powermate, I'd love to do an A-B comparison using my Genesis/Radian 6mm. Certainly if I get into digital imaging, I think a 5x PM may be on the agenda. Cheers, Fox.