Small ED/APO refractors - what are the options?

[OzEclipse (Joe Cali)]

Originally Posted by Wavytone

Ah Ok. I wouldn't bother with the small refractors - you might as well buy a pair of 70mm binoculars.

As for eclipse chasing... A whole different matter. A long time ago I had a Meade 102mm f/10 SCT with the tripod base (not the fork mount) for that purpose, a robust camera tripod was entirely adequate. IMHO it was the perfect choice - small enough to go on a plane, could be backpacked anywhere along with whatever you need, yet enough to do something reasonable.

My next choice - if you can afford it - is a Questar 3.5".

I both agree and disagree with Wavytone. I agree that, a long time ago, eclipse chasers used and favoured small SCT's or Maksutovs.

However, this is no longer the case. These days with the proliferation of reasonably priced small ED refractors, eclipse chasers overwhelmingly favour small refractors with apertures in the 60-90mm range and focal lengths in the 350mm-600mm range. A larger field allowing visual or photographic views of the outer corona with some "dark space" around it for contrast is ideal. Portability is key. If you chase a lot of eclipses, you will invariably be subject to strict luggage limits when you need to use smaller aircraft. In Svalbard last March we had a 15kg limit. On light aircraft it can be 10kg.

At one stage I was using an ED 80, 600mm fl 80mm f7.5. Now I have switched to a more compact William Optics 70mm f6.3. FL=430mm and prefer its wider field both at the eyepiece and with an APS DSLR.

Some people love binoculars for eclipses, others hate them. They are hard to support and look through comfortably unless the eclipse altitude is low to to horizon. A diagonal or flip mirror on a small refractor allows comfortable viewing for any altitude eclipse.

I use an APS DSLR with a 1.25 inch flip mirror and a parfocalized 1 1/4 inch 16mm 65 deg eyepiece so I can flip between photographic and visual during totality. This gives me a 1.9x3.0 degree photographic field and a 2.4 degree visual field in a reasonably compact package. Any of the small refractors - Stellarview, Willam Optics among many others are fine as of course are any of the premium brands.

A Meade ETX will only image the inner corona 0.7 x1.1 degree field in an APS. A full frame camera will probably vignette.

You can see examples of solar eclipse images with the 70mm f6.3 and ED80 on my website -
http://joe-cali.com/eclipses
I used the 70mm f6.3 440mmFL with APS DSLR for these eclipses
2015 TOTAL with APS DSLR
2010 TOTAL with APS DSLR

I used the ED80 80mm f7.5 600mm FL for
2013 ANNULAR with APS DSLR
2008 TOTAL with APS DSLR
2006 TOTAL with 35mm film DSLR

Cheers

Joe

[Wavytone]

Ah... joe I forgot to mention I was only interested in Baily's beads and the chromosphere - not the corona. A 0.7 degree field turned out just fine. The other aspect is full frame vs APSC dslr... I was using full frame and for 2017 probably will do again. This makes a significant difference with respect to the focal length - I agree if you're going to use an APSC sensor 500-600mm do will be plenty.

If you want the corona yes you want a wider field - and a shorter focal length.

[Retrograde (Pete)]

Originally Posted by OzEclipse

I use an APS DSLR with a 1.25 inch flip mirror and a parfocalized 1 1/4 inch 16mm 65 deg eyepiece so I can flip between photographic and visual during totality. This gives me a 1.9x3.0 degree photographic field and a 2.4 degree visual field in a reasonably compact package. Any of the small refractors - Stellarview, Willam Optics among many others are fine as of course are any of the premium brands.

Hi Joe - thanks for telling us about your eclipse setup. I also use a Pentax K-5 (aps-c)
The flip-mirror idea sounds really good and something I'll certainly investigate although I'm a little unsure how to go about getting a camera and eyepiece parfocal via this arrangement.

[OzEclipse (Joe Cali)]

Originally Posted by Retrograde

Hi Joe - thanks for telling us about your eclipse setup. I also use a Pentax K-5 (aps-c)
The flip-mirror idea sounds really good and something I'll certainly investigate although I'm a little unsure how to go about getting a camera and eyepiece parfocal via this arrangement.

Sorry I didn't explain that. The camera needs more back focus than the eyepiece. The William Optic M70 refractor's Crayford focuser has a mm scale on the barrel. I focussed the camera, took a reading, then the eyepiece then I machined my own custom extender for the eyepiece. I machined it a little short then I focus the camera, pull the eyepiece up until focused and then lock it in place for the duration. If your refractor doesn't have a scale, use a vernier caliper to make the measurements.

One more thing, With the eyepiece, flip mirror and camera on the back, it doesn't balance on the dovetail foot. However the foot can be removed and rotated 180 degrees which extends the dovetail backwards towards the camera. This reversed foot also works when I use a 2 inch diagonal and eyepieces for visual.

For travel, I prefer the M70. It fits in my carry on camera back pack with all my other camera gear and the shorter tube sits with less vibration on the small mounts I travel with. The ED80 had to travel in my checked luggage. One day in Shanghai, I watched the luggage handlers throwing my suitcase up to the luggage hold, they missed and it fell down to the tarmac. ED80 was ok. Good suitcase and padding.

They are both nice scopes. If I were recommending a car portable instrument, the ED80 would be my pick but you will want to upgrade the focuser. I got both brand new some years ago for around $500 each so I've kept them both. Use the ED80 for lunar and annular and general grab and go scope and the WO for total eclipse travel.

cheers

Joe

[dannat (Daniel)]

the Borg are great units -cheaper than Tak , 71Fl would be very good, can be bought from peter tan in HK www.tan14.com.gears.htm [cheaper than hutech]

the WO would not disappoint either

[OzEclipse (Joe Cali)]

Originally Posted by dannat

the Borg are great units -cheaper than Tak , 71Fl would be very good, can be bought from peter tan in HK www.tan14.com.gears.htm [cheaper than hutech]

the WO would not disappoint either

Daniel is correct and understated. Borg are a premium quality instrument and can be good value for money.

Be warned, the Borg are modular telescopes. You buy bits and pieces to put together what you want. This makes them very flexible but also a bit confusing. Their modular design also break down well for travel. You can carry the tube components in checked luggage and the objective unit in your carry on.

If you buy the #6071 kit HK$7200=A$1260 you get a 400f5.6 telephoto. There is a helical focuser in the middle of the train. However you'll need to buy tube rings to support it. If you want a visual scope, you'll have to buy a visual back end plus diagonal etc. Not trying to put you off Borg, just warning you to cost out all the bits and pieces before you make a decision.

I considered Borg many years ago but was buying during the GFC at a time when the A$ was very weak which made buying Borg via Hutech a relatively expensive undertaking and decided to go the William Optic route instead. If you can afford the Borg, they'll be better than the WO and that helical focusser won't sag or slip.

If you can't afford the Borg, Andrews is currently selling the MEGREZ 72 ED f/6 FD for $500. Except for 2mm extra aperture, this looks identical to the M70 instrument I have. The Focuser on the M72 is the same as mine, it's ok when tension is properly adjusted, but not great when the tension gets loose. It is much better than the awful slippery Synta Crayford focusser that came with my ED80.

The WO ZS71A at $800 is supposed to have a better 2 speed R&P focuser if you believe the advertising. I have no experience with this focuser and can't make an informed recommendation whether it's worth the extra money.

cheers

Joe

[Retrograde (Pete)]

Thanks for the info Daniel and Joe.

The Borg certainly sounds great as an astrograph but maybe not quite so functional as an eclipse scope as far as mounting options go etc.
That Megrez seems like quite a bargain but probably isn't ideal as an astrograph.
Whilst I may not be closer to making a decision I'm certainly more informed about the choices.

[glend (Glen)]

I still think the Explore Scientific ED80 Triplet ticks all your boxes. With its retracting shield the total length for transport can be only 335mm , by 140mm wide, with the diagonal and tube extension removed. It can be both visual and astrograph. It's very cost effective if you buy from Optcorp or Telescope.net and bring in directly (under the GST treashold). Gives you more flexibility in terms of use.

[Camelopardalis (Dunk)]

I've not had the chance to look through or image with a Megrez, but depending on how much weight you put on each of your requirements, the Zenithstar may or may not be good for you. The focuser is solid...I've never experienced any slippage, and with a fringe killer you can keep the blue halos minimised.

But I can't help thinking a triplet would be better all round for a little more $$. For example, the Orion ED80 triplet seems to have a good reputation. It's small, light(ish) and well corrected by all accounts.

[Retrograde (Pete)]

A quick update on this.
Whilst I was very tempted by the Borg 71fl the cost was just a bit too high to justify for the aperture I was looking at (especially once you added one of their field-flatteners at an extra $500+)

Yesterday I picked up an Astrotech 65 EDQ from an IIS member at a reasonable cost. It is pretty much the exact focal length I was after and with the in-built flattener it represented great value & should be a great little astrograph.

Down-sides are it's a bit hefty with four pieces of glass and a bit slow at f6.5 but still fits on the camera tripod and is small enough to pack in hand-luggage for travel so overall a good compromise.

[Atmos (Colin)]

I have recently been thinking about a Sky Watcher Esprit 80mm which comes with a 0.85x flattener reducer. Makes a 80mm F/4.2 wide field scope at a pretty reasonable price.

[Camelopardalis (Dunk)]

Originally Posted by Atmos

I have recently been thinking about a Sky Watcher Esprit 80mm which comes with a 0.85x flattener reducer. Makes a 80mm F/4.2 wide field scope at a pretty reasonable price.

None of the Esprit come with a reducer - it's a field flattener only. The 80mm is f/5 native. No doubt there's a reducer that would work fine though.

Congrats on the new scope Pete, should put out some might fine views

[Atmos (Colin)]

Originally Posted by Camelopardalis

None of the Esprit come with a reducer - it's a field flattener only. The 80mm is f/5 native. No doubt there's a reducer that would work fine though.

Congrats on the new scope Pete, should put out some might fine views

Thanks for that, I do remember reading recently that there was a 0.85x flattened reducer specifically for the 80mm so I assumed that was what it came with.

[Camelopardalis (Dunk)]

Originally Posted by Atmos

Thanks for that, I do remember reading recently that there was a 0.85x flattened reducer specifically for the 80mm so I assumed that was what it came with.

FWIW, Skywatcher says the field flatteners included (in Aus) with the Esprit are tuned to their scopes.

I read somewhere (a while back) that the APM reducer works well... but I'd looked at it and shrugged it off because of the price... http://www.teleskop-express.de/shop/...rs-and-RC.html

I don't have any reducers to hand so can't really test, but it'd be interesting to see if any of the generic reducers like the Orion or the TV TRF2008 worked

[Slawomir (Suavi)]

Stellarvue is about to release a new 70mm f6 triplet, that with a dedicated reducer could potentially be a very neat wide field triplet at f/4.8.

[castor]

I disagree about the statement that small refractors are near useless.

My Takahashi FS-60c provides wonderful views of the planets and sweeping views of the Milky Way and the Magellanic Clouds and the brighter DSOs. In terms of Jupiter and Saturn it can handle near 200x without image degradation. It is literally like a lightly built short person who has been on steroids.

The Orion 80ED provided immense value when it appeared and does go deeper in accordance with its aperture.

[N1 (Mirko)]

Originally Posted by castor

I disagree about the statement that small refractors are near useless.

Yep, I think everybody on this thread so far would agree with you. Even Wavy, who, instead of just one small frac, is recommending a pair of them (aka binoculars). A valid proposition. So all good

[MortonH]

Stellarvue have just announced a 70mm f/6 triplet with 2.5" R&P focuser. A bit pricey though at US$799.

http://www.stellarvue.com/sv70t-apo-triplet-refractor/

[Camelopardalis (Dunk)]

Originally Posted by MortonH

Stellarvue have just announced a 70mm f/6 triplet with 2.5" R&P focuser. A bit pricey though at US$799.

http://www.stellarvue.com/sv70t-apo-triplet-refractor/

But no doubt strategically less pricey than the WO Star71...until you add the cost of the field flattener...essential for imaging with a short focal length refractor.

[Andy01 (Andy)]

Originally Posted by Camelopardalis

But no doubt strategically less pricey than the WO Star71...until you add the cost of the field flattener...essential for imaging with a short focal length refractor.

Looks like a very nice 'scope, and Stellarvue have a great reputation.

Although by the time you add the approx $295 for the reducer/flattener, the estimated Fedex shipping cost of $185 and import costs ie: Customs entry, Airport terminal fee, Documentation fee, Currency adjustment fee, Airport fuel surcharge & GST you're looking at around $2050Au. which is rather more than what I paid for the WOStar71 that I ordered last week