Which 3x Barlow for Planet Imaging?

[Kal (Andrew)]

Fahim, not sure of you have already seen these graphs, but Televue show you the magnification level of both their barlows and powermates from 0mm through to 100mm spacing. As mentioned, you should take into account the spacing distance with your filter wheel when making your decision.

[Stephen65]

Fahim

I haven't tried. I have a TV 2.5x powermate and I use that as the next step up for more image scale.

[alela (Alejandro)]

Originally Posted by AlexN

5x powermate can be useful, but you do have to watch your focal length on nights with less than optimal seeing... I have a 2x ED Barlow, a 3x TeleVue and the 5x TV PM, and since buying the powermate, I've not used the other barlows. However my scope only hits 6m focal length with the 5x, yours would be 10m plus whatever the extension of the filter wheel adds... Thats a LONG focal length.. It would only be useful on THE best nights of the year.....

I'd say get a 2.5x Powermate or a 3x TV barlow. If you have the money to throw around, get a 5x aswell, otherwise you'll get that night of brilliant seeing and be kicking yourself that you dont have more focal lenght.

I ordered a TV 5x PM, and it scare me a bit your opinion. I also have a celestron focal reducer from f/10 to f/6.3. What's your opinion on stacking a focal reducer and the TV 5x PM in line? Will it bring nice seeing or am I loosing a lot for reduce and then enlarge focus?

Thank you,

Alejandro

[AlexN]

Alejandro, It all depends on what scope you'll be using.

a 5x powermate is much more useful to someone with a 12" newtonian than it is to someone with a 12" SCT.. The reason for this being that on nights where the seeing is less than optimal, the longer the focal length you use, the more noticeable the poor seeing will become. For example, on night recently, using my 5x powermate in my newtonian giving me a 6.3m focal length gave a very nice looking image.. On the same night however had I been using my SCT, the 5x powermate would have yielded a 14.5m focal length, at which point the image would appear to "break down" or lose quality as a result of the instabilities in the atmosphere being magnified so heavily. Had I then gone to the 2x barlow, the resulting image would be much more acceptable, due to the focal lenght coming back down to a more acceptable 5.8m...

The 5x Powermate might not be able to be used every single night of the week, however even if you only get 4 or 5 nights a year where you can effectively use it, you will not regret buying it.. as you will be rewarded on those nights with a very large image, and if everything else goes to plan, A very nice image..


I dont know how you would go with a 6.3 focal reducer and then a 5x powermate.. In theory it should work, however you're then adding another bit of glass into the imaging train, which loweres light transmission and so on... Someone more knowledgeable than myself might be able to answer that question better.

[netwolf]

Well i got a used Televue 3x Barlow on order.

Regards
Fahim

[matt]

Well done, Fahim.

I'm sure you'll be happy with it