I think the best addition I made to my Sky-Watcher Explorer 130M was a Baader Helical focuser.


It threads directly onto the focuser T-ring. This enables me to fine focus after initially finding focus with the rack and pinion focuser.


This has drastically improved image quality at magnifications of around 200x to 300x.



I had some initial problems with some eyepiece combinations as I thought I wasn't getting enough back-focus with the helical focuser threaded into the T-ring. After some evaluation I believe this was due to unfamiliarity with the focuser and the possibility that individual eyepieces weren't sitting in the compression ring correctly.



The focuser is particularly good for lunar/planetary image improvement at high magnifications.


Enabling me to more easily resolve Uranus into a bright little cyan disc during last night's conjunction.

 

Thank you for the info regarding the Baader Helical-Focuser - I think I'll take a hunt about over here for these. I have a 2-piece BORG one - which I keep in reserve for any super-fine tuning I may run into being needed. But it's getting rather dusty since I converted most everything into dual-speed Crayford-Focusers. I was pleasently surprised by how well these upgrades worked out. The only scope I haven't put a dual-speed on is my older 1.25"- format 200mm F/4 Rich-Field Newtonian. It would require major-surgery to the OTA to do so.

Just a humble one-speed Crayford, in 1.25", is on her now - up from a pretty good R & P 1.25" that came in as stock-focuser in 2000, or thereabouts.

Here's to Tinker-Toys to astronomers!

Dave

 

I found that it took me longer to suss out than I assumed it would. Like many things Baader, it has three set screws pressing the compression ring. This is probably a brilliant idea in theory as it can help to keep the eyepiece from canting, but in practice it can be a bit fiddly in the dark. Furthermore there is a fourth set screw which tightens/loosens the helical movement. Again, a good idea, but in the dark it's easy to turn the wrong screw. I find that lightweight GSO style aluminium draw tubes with safety undercuts can be difficult to extract and as the set screws aren't captive I worry about one dropping out if over loosened. It can also be used on my Omegon diagonal used in conjunction with a T-adaptor.



It might look a bit 'Heath Robinson' but with a small enough eyepiece it works. I guess I won't be using it like that with my 10mm Delos. lol

 

I think it should be fine in a diagonal, the Luminos isn't that heavy. I regularly put a 16mm Nagler and a 19mm Panoptic on top of a TeleVue Powermate in a diagonal.

 

The X-Cel 2x Barlow is a 'shorty' type. It's pretty solidly made though and a lot of people prefer the shorties in a diagonal as it sits lower. The undercut isn't very deep and I haven't had any real problems extracting it from anything. TeleVue don't make a short Barlow as they don't believe that the short type have a sufficient light path or something like that.


The X-Cel is Chinese made, undoubtedly commissioned by Synta, but I don't know who the actual OEM is. It is an apochromatic though and pretty high quality. I haven't noticed any obvious vignetting when using it compared to the longer TeleVue 2x Barlow.



I think the TeleVue has a higher build quality and overall it's probably the better Barlow, but there are times when a 'shorty' Barlow is preferable.



I've got a few Barlows/amplifiers and when I was looking for a short, sturdy, well made and high quality 2x Barlow, preferably with an undercut, the X-Cel seemed a logical choice.

 

The relatively inexpensive Celestron (GSO) achromatic Barlows, like the Omni 2x Barlow and similar Celestron kit Barlows, can actually have their draw tubes unthreaded. This can facilitate cleaning the upper surface of the Barlow lens which can be a little inaccessible otherwise. As far as I know the Barlow element itself can't be removed, as in some other Barlow designs.



It can also facilitate the modification of eyepiece focal lengths if the detached draw tube/Barlow unit is threaded onto a compatible eyepiece. Turning this 15mm Omni Plossl (above) effectively into a 9.3mm eyepiece.



Likewise, the 12mm Omni and 17mm Celestron Plossls above have been converted to 7.5mm and 10.6mm (approx) respectively. This process also lengthens the eye relief.

 

I've removed the lens-cell from an Orion Shorty 2X Barlow and gave it it's own, little case. I use this to thread into an eyepiece-barrel that I'd like to boost it's magnification by 1.5X (or 1.6X? Who knows...?). I reserved it's body & barrel for use if I need to extend my focus on something, in 1.25" format, sometime.

Enjoy,

Dave

 

Barlows and removable lens cells don't seem to have a great deal of consistency. TeleVue 2x & 3x Barlow elements unthread, and I believe can be threaded onto each other's Barlow bodies, but TV Barlow elements won't thread into the bottom of eyepiece draw tubes (even TeleVue ones). I think the element can be removed from the 2.5x Powermate. The Omegon (Barsta) 2x Short Barlow I have has a filter thread but as far as I can see doesn't have a removable element. Apparently the apochromatic short Barsta Barlows have Japanese glass, which wouldn't surprise me as mine is as good visually as any of my TeleVue Barlows. In fact, the Omegon/Barsta and the TeleVues are visually the finest Barlows I've used. The prices can vary on the differently branded Barsta Barlows though, and I think I paid a bit over the average for the Omegon version.



I believe there is a 3x version as well. I've seen them marketed under a variety of brands, including TS Optics, Omegon, Sky-Watcher and 365Astronomy.



http://www.barsta.com/show_hdr.php?xname=MDA8V11&dname=OPFOR71&xpos=6

I have a TS Optics (GSO) 2.5 Barlow, although I'm not sure if it's actually apochromatic or not as there seems to be some controversy over that. I don't know if the element detaches yet lol.

 

Yes - you're quite right regarding the TV 3X (and 2X) Barlows not having threads that play well with others. My Orion Shorty is really a GSO, and fits a great many others. I'm not sure if I've ever tried threading it into a TV-eyepiece. I'll give that a try the next time I dig out one of my TV's.

Onwards & upwards,

Dave

 

It's not just that the TV threads don't play well with others, the detached TV Barlow element is physically the wrong size to thread into anything else. Which is a bit weird. lol

 

Which one was the 2x HPS Ray? The TV 2x is on sale at Agena: http://agenaastro.com/televue-1-25-2x-barlow-blw-2125.html

 

Was your High Point Scientific Barlow GSO like my TS Optics version below?


That's one of the problems of placing a Barlow in a diagonal. It can get a bit tall. The X-Cel 2x Barlow is high quality though, I can't really fault it. Depending on what scope I'm using and what eyepiece is going into the Barlow, I tend to vary what I'm using.

I don't know much about broadband interference filters, was there a specific one you were thinking of getting?

 

I've never heard of the filter you reference, Ray. But I'm on my way now to find out!

Hang in there - before looking at our star.

Dave

I'm back:

STOP! THERE IS NO REFERENCE FOR VISUAL USE!
This means these are not for use for visual-usage. Please give us a link to this item before paying down and acquiring one. I can't even find a website to give me technical specs on these without creating an "account." I read that as meaning there is something mighty bad going on behind the scenes.

Dave

 

I think you're right about this Dave, I googled broadband interference filters as I hadn't heard of them either, and all I got was references to telecommunications. I assumed 'Broadband Interference Filter' was some marketing title of an esoteric filter of some sort. I don't know anything about solar viewing though. I've forgotten what the Sun looks like anyway lol.

On a lighter note, I've been daylight testing these three Celestron 2x Barlows. Someone suggested to me that the (possibly Synta-made) Barlow here on the far right was slightly better quality than the other two (almost certainly GSO-made) 2x Barlows.



The two black coloured Barlows were from Celestron kits, the silver coloured one is a Celestron Omni 2x. The one with the T-adaptor has an unthreadable Barlow element and a chrome plated brass smooth draw tube. The other two have aluminium draw tubes with undercuts. The aluminium draw tubes themselves can be unthreaded. The Omni and the Celestron T-adaptor are about the same price both sides of the pond.

The thing is ... looking through them, they all seem to be the same quality. Pretty decent for what they are and cost.