3 x Barlow with t-thread for imaging Mars

[Relpet]

I'm in hibernation in southern England at present.  Might as well be curled up underground for all I've seen of the night sky since November.  However as I am still in my initial year as an astronomer I'm getting pretty excited at the prospect of being up close and personal with Mars for the first time under clear French skies in early summer.  I have a cheap webcam-type camera and enjoy the use of a Nikon D5100 dSLR.  I have an 8" Dob and a NexStar 4se (new to me. Bought s/h in November and not left the house yet!).  I have a GSO 1.25" x 2 Barlow with a T-thread and an ES 2" 2 x Barlow for the Dob but would like a good quality 3 x Barlow with a T-thread to use with the NexStar. That would be my first experience of a tracking system for imaging also.   All my searches on this forum and elsewhere keep uncovering gear that is either out of stock,  no longer available, or hugely expensive.  £60 is about as far as I can go.  Any suggestions or advice would be warmly welcomed.

[MarsG76]

You did say you wanted a high quality 3X barlow, the only one I can recommend to you as the best I have used is the Televue 3X Barlow.. although it's a bit more than £60... But you definitely do get what you pay for.

[riklaunim]

Televue is not the only choice and may not differ in any way from GSO

Also note that this DSLR has 4.78 µm pixels, which reach optimal resolution at f/17-24 so a 3x Barlow with a f/10 SCT would give f/30 which is too much (unless you bin pixels).

[Davey-T]

As per Rik, I use a DSLR  on f/10 SCT and 2X Powermate and don't think I could push it to more magnification, even using the 1X1 640X480 crop video mode Mars is a tricky bouncing orange ball.

Dave

[Relpet]

Thanks for the technical advice.  Looks as if I'm barking up the wrong tree so will stick with what I've got for the meantime.

[Dave In Vermont]

What I tend to suggest is saving up your ¢'s for a top-drawer Barlow, or PowerMate. And TeleVue is the one I usually recommend. I hate to have to stoop to suggest a TV as I don't wish to sound elitist, but when it comes to Barlows - or their tele-negative cousin the PowerMate - you really do want to go that route. There's nothing worse than a cheap Barlow that announces it's presence in the optical-train with whistles & trumpets.

The best Barlow, which is worth the wait, is one that vanishes in the pathway. Like it's not there at all. Just a bigger image with all the subtle detail you want. And no vignetting or dimming along the way. And the TeleVue Barlows aren't really that much more ££-wise. Hence the word 'saving.' The other road leads to a drawer full of cheap Barlows that never see the light of day/night. Or ends up in the Used bin on eBay. And the reason for a Barlow vanishes from sight out of pure disgust.

I started with cheap Barlows when I was young. And it took me many years to try again with a TeleVue. And I was amazed! The poor quality Barlow I had as a kid had so warped my view of these things, I didn't have high hopes for any Barlow ever. But once I saw what a good Barlow could do - I no longer hated all of them! I've since tried a few others that have come my way. Most inexpensive Barlows aren't bad these days. But I wouldn't think about Barlows at all if I hadn't had that first look through a top-quality one. Thus my suggesting saving up. There are other excellent brands aside from the TV's. But I'll let someone else sing their virtues. But on to Mars.....

Look into colour filters for Mars. I was shocked at what one did for my view back in 2003, when Mars put on it's best show forever! An off-yellow special Martian-filter from Sirius really made the polar-caps stand out like two tufts of cotton through my 5" refractor. As well as allowing sharp separations of the maria. Then a planet-wide dust-storm rolled in and the party was over. But I'll never forget!

Good luck on Mars this time!

Dave

[Relpet]

What I tend to suggest is saving up your ¢'s for a top-drawer Barlow, or PowerMate. And TeleVue is the one I usually recommend. I hate to have to stoop to suggest a TV as I don't wish to sound elitist, but when it comes to Barlows - or their tele-negative cousin the PowerMate - you really do want to go that route. There's nothing worse than a cheap Barlow that announces it's presence in the optical-train with whistles & trumpets.

The best Barlow, which is worth the wait, is one that vanishes in the pathway. Like it's not there at all. Just a bigger image with all the subtle detail you want. And no vignetting or dimming along the way. And the TeleVue Barlows aren't really that much more ££-wise. Hence the word 'saving.' The other road leads to a drawer full of cheap Barlows that never see the light of day/night. Or ends up in the Used bin on eBay. And the reason for a Barlow vanishes from sight out of pure disgust.

I started with cheap Barlows when I was young. And it took me many years to try again with a TeleVue. And I was amazed! The poor quality Barlow I had as a kid had so warped my view of these things, I didn't have high hopes for any Barlow ever. But once I saw what a good Barlow could do - I no longer hated all of them! I've since tried a few others that have come my way. Most inexpensive Barlows aren't bad these days. But I wouldn't think about Barlows at all if I hadn't had that first look through a top-quality one. Thus my suggesting saving up. There are other excellent brands aside from the TV's. But I'll let someone else sing their virtues. But on to Mars.....

Look into colour filters for Mars. I was shocked at what one did for my view back in 2003, when Mars put on it's best show forever! An off-yellow special Martian-filter from Sirius really made the polar-caps stand out like two tufts of cotton through my 5" refractor. As well as allowing sharp separations of the maria. Then a planet-wide dust-storm rolled in and the party was over. But I'll never forget!

Good luck on Mars this time!

Dave

Hi, Dave,

Happy New Year, by the way.

The TV Barlow does come up from time to time second-hand so I will be vigilant in following your advice to wait for something special.  In my 76th year I can't wait too long, you understand!  My ES 2" Barlow works fine in the Dob but I do need something better in the smaller size for the Celestron.  Your description of your first view of Mars is enticing.  Fingers crossed.

Best wishes

Peter (aka Fang)