William optics barlow

[Robindonne]

To keep the question flow moving i have another rookie question.  I bought some months ago an old william optics barlow.  A 2”.  I immediately ran into a problem of not getting any focus with an old zenithstar 80. I dont have any extension tubes or something like that. But is that what i need to get focus? Because the barlow itselfs is like 12 cm long. Or should i just sell it and use smaller eyepieces?

Edited April 29, 2020 by Robindonne

[John]

I understand that the William Optics 2.5x 2 inch barlow lens requires quite a lot of additional inwards focuser movement to allow it to reach focus. Adding extension tubes won't help - that just makes matter worse.

I have read about other people having issues getting this barlow to focus with their refractors. Not sure there is an easy solution

 

[Robindonne]

Ah ok.  I couldn’t remember what direction i came in short. Thx.  

[Louis D]

See if that bottom section unscrews and contains all the lenses.  If it does, see if it will thread onto the end of your diagonal like a filter.  You should be able to reach focus in this configuration, but at a higher magnification factor.  I know the GSO 2" ED 2x Barlow can be used in this manner.

[Robindonne]

Ow not that bad of an idea.  A short moment of thinking of cutting de 2” tube shorter if really unusable was immediately deleted because damaging it and not get getting any closer because of the barlow thickness itself.  Wouldnt gain a mm with that.  But directly attaching might help.  Ill try and let it know.  Thx

[John]

Bear in mind that you probably won't get 2.5x doing it that way. Probably more like 1.5x but the exact amplification will depend on the focal length of the barlow lens and the distance between the eyepiece lenses and the barlow lenses.

 

[Robindonne]

16 minutes ago, John said:

Bear in mind that you probably won't get 2.5x doing it that way. Probably more like 1.5x but the exact amplification will depend on the focal length of the barlow lens and the distance between the eyepiece lenses and the barlow lenses.

 

Ok i will.  It looks like its an mostly unsatisfying buy😬.  The first thing i noticed was that the lens itself was more like an 1,25 inch size.  But maybe its common with 2” barlows. I dont know.  But all these efforts instead of using the powermate for example is probably gonna make the wo apo-barlow a collectors item in the way of not having any other purpose then collection

Edited April 30, 2020 by Robindonne

[Louis D]

Look for the GSO/TPO/Apertura/Zhumell/AstroTech/TSOptics/Revelation 2X ED 2" Barlow.  It is really good for the money, is full aperture, has an excellent 1.25" adapter included, and the optical nosepiece is 2" filter threaded so it can be screwed directly onto 2" eyepieces for about 1.5x or onto the end of a 2" diagonal for about 3x.  If you can locate a used Tele Vue Panoptic Barlow Interface (PBI), it works very well with this Barlow to make a poor man's Powermate because the GSO Barlow has almost exactly the same focal length as the TV Big Barlow the PBI was intended to work with.

[Robindonne]

Ok thx i will have a look.  Although i bought some months ago a complete set from a retired passionist.  Which also included a powermate. 1,25”.  But the gso brand and its other branded products do seem to work well.  Ill think about it. Thank  you again

[Robindonne]

10 hours ago, John said:

Bear in mind that you probably won't get 2.5x doing it that way. Probably more like 1.5x but the exact amplification will depend on the focal length of the barlow lens and the distance between the eyepiece lenses and the barlow lenses.

 

Oh and John, a little off topic but okay, i once advertised an c5+ on this forum.  For sale or to swap.  And remember you telling me to not need an apo because the c5+ is some sort of, or is, an apo.  The scope is still for sale and biddings came from 50,- to 600,-   I received like 10/15 mails asking me to sell for 600,-  people who were not on a hunt for a scope but were willing to add that white celestron to their arsenal.  Maybe its not worth more then that. I dont know.  And still dont use the c5.  But you told me the set was fine, the accessoires were plenty to start with etc etc.  And when reading all these messages from ex-owners who were sorry they sold this scope in the past, im really thinking of keeping it for moments with family or my kids to look back in time through a scope that was also made back in time. My only (semi)apo refractors i own are a 71 and 80 mm zenithstar.  Do you still think its not worth to search for an used 100 or 120 mm apo to complete my own collection, keeping in mind that we always will carry a shoppinglist of items we terribly need😅, or do refractors have some pro’s to consider over using a sct?   Ill probably keep the c5.  But your comment made me think about the terrible need for a medium to big apo.   Thx for reading a long and boring question

[John]

9 minutes ago, Robindonne said:

Oh and John, a little off topic but okay, i once advertised an c5+ on this forum.  For sale or to swap.  And remember you telling me to not need an apo because the c5+ is some sort of, or is, an apo.  The scope is still for sale and biddings came from 50,- to 600,-   I received like 10/15 mails asking me to sell for 600,-  people who were not on a hunt for a scope but were willing to add that white celestron to their arsenal.  Maybe its not worth more then that. I dont know.  And still dont use the c5.  But you told me the set was fine, the accessoires were plenty to start with etc etc.  And when reading all these messages from ex-owners who were sorry they sold this scope in the past, im really thinking of keeping it for moments with family or my kids to look back in time through a scope that was also made back in time. My only (semi)apo refractors i own are a 71 and 80 mm zenithstar.  Do you still think its not worth to search for an used 100 or 120 mm apo to complete my own collection, keeping in mind that we always will carry a shoppinglist of items we terribly need😅, or do refractors have some pro’s to consider over using a sct?   Ill probably keep the c5.  But your comment made me think about the terrible need for a medium to big apo.   Thx for reading a long and boring question

I honestly can't recall that advice but I have made quite a lot of posts here over the past 15 years so perhaps thats not surprising !

It might be worth starting another thread on the differences between a C5 and a 100mm or 120mm apo / ED doublet refractor.

I'm probably biased now because I do have an ED120 and I've not owned a  C5 for quite a while

The C5+ if I recall was a particularly nice version of the C5 with a table top motorised mount. A sort of complete portable and compact instrument. An ED120 is a great scope but can't match the C5 for compactness and portability.

 

[Robindonne]

Ha okay.  Maybe i will one day open a topic about the pros and cons of small sct over apos.  But it was definitely you who commented.  I remember the guy standing next to a colossal white dobson😅.  But ok.  Somehow i know big refractors must have something extra over. Sct.  Why would one buy an expensive piece of equipment when better results can be achieved with a much cheaper and lighter small sct.   Cant tell the answer for now but maybe i ask one day.  Im sure someone will explain in full color.  Thx.