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Old 17-07-2019, 01:57 AM
Aron
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Question Skywatcher 72ED accessories?

Planning to purchase this scope. So I'm aware that you need to get some kind of extension to reach focus with DSLR? what kind of extension tube do I need to get it into focus?

also wouldthis work as a 1.25" adapter?
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Old 17-07-2019, 06:56 AM
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The_bluester (Paul)
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To get a decent looking field you really need the reducer/corrector that goes with it, that brings (If your reducer to sensor distance is right) the focus point in within the range of the original focuser travel.


When I bought mine they had not figured out how to attach the reducer (It is the one for the ED80 in fact) so I had to get an adapter made, but Skywatcher has released one to fit now. The ED80 had an external thread on the focuser drawtube and the ED72 an internal one, I am still mystified by that decision. Apparently apart from that detail they are essentially the same focuser.


From the reducer you would need a 48m to T thread adapter and then T ring spacers and T ring to camera adapter if required to get the spacing right.

Last edited by The_bluester; 17-07-2019 at 08:45 PM.
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Old 17-07-2019, 07:31 PM
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I wouldn't be without mine, used for nature and Ha
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Old 17-07-2019, 07:33 PM
Ukastronomer (Jeremy)
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Quote:
Originally Posted by The_bluester View Post
To get a decent looking field you really need the reducer/corrector that goes with it, that brings (If your reducer to sensor distance is right) the focus pointin within the range of the original focuser travel.


When I bought mine they had not figured out how to attach the reducer (It is the one for the ED80 in fact) so I had to get an adapter made, but Skywatcher has released one to fit now. The ED80 had an external thread on the focuser drawtube and the ED72 an internal one, I am still mystified by that decision. Apparently apart from that detail they are essentially the same focuser.


From the reducer you would need a 48m to T thread adapter and then T ring spacers and T ring to camera adapter if required to get the spacing right.

What adapter is available now ??
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Old 17-07-2019, 08:57 PM
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The reducer/flattener for the ED72 is actually the ED80 one, but for some reason they used an internal thread on the ED72 focuser drawtube versus an external thread on pretty much everything else they make with a 2" drawtube. Meaning the reducer does not just screw on to the focuser like it does on the 80mm.

You can screw a 2" nosepiece into the reducer but with the compression fitting (As you are using to attach your diagonal) you cant quite get enough focuser in travel to achieve focus with proper reducer to sensor spacing. I modified the compression fitting to shorten it and get it to focus but the nose and comression fitting give tilt issues (Different tilt every time you took it apart!) so I had a threaded adapter made which is M54 male on one side (To go into the focuser drawtube) and M56 male on the other to go into the reducer with a narrow shoulder.

Skywatcher have now released an adapter much the same, IMO they should have had that ready when the scope was released. Mine is off being modified at the moment to accept an M48 thread filter cell inside it as my camera really benefits from a UV-IR cut filter and it is a handy way to hide it up in the drawtube where it does not complicate sensor to reducer spacing, just a slight change in focuser position.


Give me a bit and I will put up a pic.

Edit, pic added, all you can see of my adapter is the knurled shoulder between the drawtube and reducer.

I will also add, if anyone else gets one made, take careful measurements of if you can, get your focuser to whoever is making your adapter. The drawtube is to an M54 thread what a cow is to a paddock, not very much the same at all. Some of the Skywatcher fittings are astoundingly poorly specified. Making the adapter to M54 meant Josh on these forums ended up remaking it for me (For which I thank him) as the "Right' thread is so loose a fit in the drawtube I put a couple of wraps of teflon tape on it for fear of popping the threads if I tightened it a bit much, the original compression fitting is much the same in fact.
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Old 18-07-2019, 10:22 AM
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Another way is to get a 2 inch nosepiece that screws into the reducer/flattener then just plonk it into the drawtube like an eyepiece. I have an orion field flattener which is identical to the skywatcher ones but shedloads cheaper with the nosepiece that does not require screwing. It's suitable for 72/80/100 and 120 ED's
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Old 18-07-2019, 10:34 AM
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Not doable without modification with this scope. The compression fitting adapter that screws into the drawtube is too deep and with the correct spacing between reducer and sensor it won't come to focus. Basically the reducer has to be up within a couple of mm of the end of the drawtube and the supplied compression fitting is about 12mm long.

I modified mine to reduce that spacing but to be honest I would recommend using a threaded adapter like I have had made (Or just buy the Skywatcher one that is now available) as the compression fitting and nose had no end of tilt issues, every time you took the reducer out and re fitted it the tilt was different.

I hate sensor tilt issues! I am going to be spending some money soon to buy a different OAG to make it threaded fittings from end to end as the camera side fitting of the Orion thin OAG I am using now is just not rigid enough, if you tweak the camera body up and down you can see the movement in it, that is my last "where is it coming from now" tilt issue.
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Old 18-07-2019, 05:09 PM
Hoges (John)
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I use the Orion Field flattener for short refractors - this both adds the extra length required to reach focus and gives a much better field. It has a thread on the camera end which screws straight into the t-mount adapter. I seem to remember a 50mm extension tube and 2 - 1 1'4" adapter was too long to reach focus with the camera. It's a nice little scope but there's certainly a bit of color if you push it - it's not as good as the ED80 (at least my example isn't).


Skip to the 3 min mark and I'm talking about focussing a DSLR.... https://youtu.be/TfZmL0XfTJk
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Old 18-07-2019, 08:03 PM
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I was planning to get ED80. After all the total costs of 72ED, with all accessories-field flattener, extension, diagonal, etc will cost me an 80ED.But I found out that the 80ED is much heavier and bulkier than I thought when I handle it, so I'm just planning to get this one for portability.

I'm using an old non full-frame canon (500D), I'm not sure how much field curvature will it show. I've seen the photos taken with full frame DSLR and the field curvature seems pretty bad though.

So I think I need some kind of extension tube of some sort?

Otherwise I'm planning to use a 2" to 1.25" reducer+1.25" diagonal instead. Saw some in travel adapter on bintel which is quite interesting.
https://www.bintel.com.au/product/te...v=6cc98ba2045f
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Old 18-07-2019, 08:11 PM
Hoges (John)
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You should only need the in-travel adapter if your 1.25" diagonal has a longish light path. My 2" diagonal works fine for eyepieces. See the vid I mentioned to see about what you'll need to focus your camera. If you're getting the field flattener - you shouldn't need to get an extension tube as well (at least not with the Orion flattener) But you'll need a T adapter for your Canon.
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Old 18-07-2019, 08:21 PM
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I've seen that 50mm extension tube with that separate t-adapter ring, but bintel only sell either 50mm or 35mm.

I think this one would fit then?
https://www.siderealtrading.com.au/p...ptical-length/

I'm thinking of getting a 1.25" adapter, so I assume the in travel one would be better than the low profile one.
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Old 18-07-2019, 09:14 PM
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Field curvature was obvious with my ASI294 and they are only a 4/3 sensor. I only took one shot without the reducer to see what it was like.



With one of those you need to look at the sensor depth of the DSLR to get the spacing right from a reducer, if it is 45mm then you only need another 10mm for the Skywatcher reducer, which would not be much more than an M48 camera adapter screwed to the reducer nose.

Last edited by The_bluester; 19-07-2019 at 06:43 AM.
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Old 18-07-2019, 10:07 PM
Hoges (John)
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The 40mm 2" to T42mm that you've linked looks good and I would be very surprised if your Canon was more than a couple of mm different to my pentax. However, if you are going to do any serious photography, I'd spend the extra $120 on the flattener instead. You don't need both as the Orion flattener puts the camera in the right spot. The 1.25" adapter looks good too - although it may not be necessary depending on your diagonals.
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