Barlow for 13mm Ethos

[jonstarrysky]

I gather that the 1.6x 2" Antares barlow (amongst others) works well with the 13E so I am thinking about buying this barlow as budget alternative to 8E. Can anyone suggest a UK supplier for the Antares Barlow ??

Also has anyone tried 13E + Artares 1.6x with a visual paracorr in place as well ? Is this collossal 3 piece train feasible re. metal crashing into expensive glass ? I guess the Paracorr tuntable setting stays the same. My main thinking is convenience of being able to leave the paracorr in all the time.

Also another ethos barlow senario I've seen involves attaching certain barlows to the 1.25" end of the 13E via the screw filter thread. This combo then slips into the focusser uning the 2" barrel adapter of the 13E. The combo therefore sticks out no more than the 13E on its own. See link below for what this looks like:

http://stargazerslounge.com/attachments/equipment-help/19275d1235403271-barlow-dob-ethos-ethos-8-ac710.jpg

Astro Engineering in the UK make Barlows like this where it can be screwed on as an alternative to the usual method. Wondering if there was any feedback on this method.

[johninderby]

Hi

I had the 13m Ethos - Antares 1.6x 2" Barlow - Visual Paracorr combination and found that while it worked it was just too long and awkward and more importantly HEAVY !

I sold the Antares 2" barlow and Parracorr and now use the AE AC710 1.25" Supreme 2x APO photovisual barlow as the barlow element can be unscrewed and put on any eyepiece making it a 1.5x barlow. Also bought the Baader MPCC. The new combination fits right into the focuser and more importantly hardly weighs any more than the Ethos on it's own, so I don't have to rebalance the dob.

The Antares 2" barlow does work very well, but is not as good as the AE 1.25" barlow so I'm actually gaining in performance. The Paracorr and MPCC are equal in performance. The Badder 28mm and 14mm fine-tuning rings put the MPCC at the correct distance from the eyepiece and still gives enough clearance to use the 1.25" barlow element. This combination is also right for the 6mm and 8mm Ethos. The new combination actually saves over one pound in weight !

I also bought a Mogg 0.3x 1.25" Extension Tube as this can be used in-between the 1.25" barlow element and the eyepiece to make it a 2x barlow, although the MPCC won't fit as well of course.

Unfortunately both the Antares 1.6x 2" barlow and AC710 1.25" Supreme 2x APO are only available from Scopes'n'Skies, not my favourite astro dealer but there seems to be no other choice.

I'm very happy with the combination now.

John

[jonstarrysky]

Thanks John.

Re. Scopes n' skies, your feelings are shared by others.

I got the 2" Antares in the end for that heavy weight combo. And what is probably similar to the bit from the AC710 that you screw onto your Ethos. This may come in handy for me as well, and is very cheap. It probably wont work with paracorr tho.

Specifically: Astro Engineering AC555 Magni-Max 1.6x thread on Barlow lens

Re. weight my XT10i can handle the Paracorr + 26T5 which is probably similar in weight to Paracorr + 13E + Antares 1.6x. Err..maybe not.

Yes, your set up sounds smarter !

[johninderby]

Hi

I have one of the AC555 Magni-Max and have tried it and actually it's not too bad for a simple doublet achro barlow, better than expected and a bargain at that price. It would hit the lens in the Paracorr, although you could probably use a Parfocal ring (or two) on the Ethos as a spacer to give enough clearance. With a bit of careful measuring perhaps?

The AC710 APO barlow is a bit more expensive than a Televue barlow (and I can't tell any difference in performance) but has the advantage of the removable barlow element. I haven't had chance to really test it properly yet but it is noticeably brighter and sharper than the Magni-Max which you'd expect at the price difference.

John

[jonstarrysky]

Thanks for the info on AC555. That order is cancelled now ! A miracle that they answered the phone so fast.

I'd be interetsed in how you get along with your AC710. They claim it beats any competition, but has yet to be tested independently. I have no reason to doubt them especially after what you say. What do you make of the way eyepieces attach to the AC710 for 2x mode ? There is a ring device rather than a screw. It is also neat how you get 1.5x plus 2x and the versatility to screw to bottom of eyepiece, when you need to keep things compact. But as you point out no good with paracorr and the tuntable setting would also be different. With the antares 1.6x sitting closest to the focusser the tuntable setting shld be the same and no dangers (except for the whole scope sinking into the ground with the weight !).

[johninderby]

Hi

I would put the AC710 as being tied with the Televue 1.25" barlow, which means it's about as good as it gets in barlows. If only Televue had made the barlow element removable. The problem with the AC710's clamping ring is that it won't work at all with the William Optics type tapered barrels. It can't clamp tight enough to contact the tapered part of the barrel, which means you'd have to pull the eyepiece half way out so that the clamp would be on the straight part of the barrel. Works fine with standard eyepiece barrels though.

I had the 8mm Ethos as well as the 13mm but sold the 8mm (for nearly what I paid for it) and got the new 6mm Ethos. With the 1.5x it now gives me 4mm, 6mm, 8.6mm and 13mm and if I use the little 1.25" barrel extension on the 6mm there's 3mm as well which pretty well covers things at the higher powers.

John

P.S.

All you need now is a foot thick reinforced concrete pad to put the scope on with the Ethos, 2" barlow and Paracorr and your all set.

[jonstarrysky]

13E + 6E + 1.5x Barlow is giving very impressive focal length coverage as you point out. Is coma correction actually needed when you barlow the 13E ?? Perhaps increasing the magnification is going to alleviate the need for coma correction.

ALso if I try the heavyweight option is the Antares best placed nearest the focusser ?

For your MPCC setup it looked like the barlow fits between the eyepiece and the MPCC as the MPCC and fine-tuning rings are all 2" but the barlow is 1.25"

[johninderby]

The MPCC is really only needed with the 13mm, but helps a bit with 13mm +1.5 = 8.6mm. The 6mm doesn't need it.

Televue recommends putting a 2" barlow into the focuser first, but as the Antares is very short it will fit into the Paracorr when the tuneable top is set to the correct setting, but I think it can just contact the Parcorr lens if turned all the way down so you have to be careful.

That's correct. With the Baader fine tuning rings on the 2" barrel, which are needed anyway to set the MPCC at the correct distance from the eyepiece, there's enough room to fit the 1.25" barlow element in-between the eyepiece and the MPCC. Very neat and compact.

John

[jonstarrysky]

John, using the barlow part of the AC710 screwed onto the Ethos, do you think this combo can be inserted into paracorr safely ??? And will the best tuntable setting change (or still be feasible) ???

At the minutre I dont want rid of my paracorr, but the heavy combo with the Antares is worrying me.

[johninderby]

Hi

It's too long if inserted directly into the Paracorr but if you use the 1.25" to 2" adaptor then it's no problem as there is plenty of room, as in this photo with the AC710 and 1.25" adaptor. Not sure about the correct setting but Televue says that a 1.25" barlow will work when used with the 1.25" adaptor and don't give a different setting.

John

[jonstarrysky]

Thanks for the picture. Think I'd prefer the security of the 2" collar of the Ethos being used rather than its 1.25" inner bit with a 2" adapter. And presumably the AC710 + 1.25" adapter combo adds length in the same whay you'd be adding length with Antares 1.6x attached to the Ethos 2" collar. So for sticking with paracorr the Antares may be best for me. My XT10i takes the Ethos & Paracorr combo in its stride, so I cant see the Antares 1.6x in there too causing too much probs.

I can see the AC710 comes into its own with your smart combo with MPCC. Or when coma correction isnt being used at all. No length is being added then.

Interestingly I see ppl using the Antares positioned between the Ethos & paracorr (against Televue's instructions that you mention). This will be increasing the separation between Ethos's field stop & Paracorr so the optimal Paracorr settings will be different. But for conveneince it will presumably be better and is keeping the more substantial bulk of the paracorr closest to the focusser.

[johninderby]

I think that with your Paracorr the Antares 2" barlow may be more straight forward, and cheaper as well, so I think that's the way to go. As you say while the AC710 is ideal with the MPCC but there's no real advantage in using it with a Paracorr.

Re: Scopes'n'Skies

Although they're not my favourite astro dealer, I did order something from them on Sunday (free shipping), got a shipping confirmation email on Monday and it arrived on Tuesday. OK it was only a small purchase, but it still came as quite a shock to get fast efficient service from them. Very disconcerting.

John

[jonstarrysky]

same here. They are great where there are no complications and can be fast. But at one point last Winter they were literally not contactable by any means for weeks, no email, no phone. That really annoyed me. Consistently ignoring all emails and not picking up the phone is bad form. They should not provide an email address. It was related to the christmas rush and presumably understaffing. Now they are better at answering the phone. They also have a habit with me of when items are out of stock to give you what they percieve to be subsititute alternatives without asking you.

[jonstarrysky]

One option is to get the 8mm Ethos (sigh...). This is simple, light (and yes expensive). Faffing about with barlows & paracorr in the dark may become a drag. Then the cheap 1.6x barlow can get me a virtual 6mm Ethos for the occasional requirement of that magnification eg: when a planet is putting on a good show. 200x may be tricky on a dob and with typical atmospheric conditions etc I think I'd prefer it that way round to getting 6mm Ethos with the barlow getting me a virtual 8mm. The 8mm would get used more (=150x).

By the way, can you advise me on good places to sell EPs in UK ? I have a nearly new Pentax XW10, boxed, even sales reciept. If I can get a fair price for it it might have to go to help justify another Ethos.

[johninderby]

The 5mm Nagler was my most used eyepiece, which is why I sold the 8mm Ethos and replaced it with the 6mm as I thought that it would get more use. I prefer not to use barlows, but the 1.25" one is easy to add to the 13mm Ethos and it still fits into a 2" diagonal.

I sold some Naglers on eBay recently to pay for the Ethos eyepieces and most went to Europe where the exchange rate worked in my favour, so for selling expensive eyepieces eBay is the easy way to get into the EU market. SGL's not bad and there's always Astro Buy&Sell but it seems to have more than it's share of dodgy buyers.

John

[jonstarrysky]

Did the 6mm Ethos live up to your expectations after selling the 8mm ??

The 6mm will get me 200x in my 10" dob which may be OK but at the limit. Certainly the 6mm barlowed will be painful on my scope (which hasnt got "buttery smooth" azimuth bearings). So I may as well get the 8mm so in total I have 13 (native), 8 (native) and 5mm (1.6x barlow). This will involve the minimum of barlow fussing as the 5mm setup would be used least.

I dont want to barlow from 13mm to 6mm with a 2" extension tube. With paracorr in place we really are talking crazy.

Cheers for the advice on selling.

[johninderby]

The 6mm Ethos is every bit as good as the 8mm, no difference other than the fl of course.

The 6mm will mainly be used in my 14" dob, but as that has the ServoCAT system with tracking, very high mags can be used. On lunar the 6mm barlowed to 3mm or 4mm gives amazing views.

John