dawson Posted March 17, 2013 Share Posted March 17, 2013 Two questions: 1. Would it be possible to wedge my alt-az mount (or tripod) and just use the azimuth motor to track objects? 2. Are equatorial fork mounts good enough at tracking (and avoiding field rotation) to be used for imaging deep space objects? These questions stem from some articles I've just been reading by Dan Lessmann (http://www.danlessmann.com/Articles.htm) Thanks James Link to comment Share on other sites More sharing options...
Brantuk Posted March 17, 2013 Share Posted March 17, 2013 Yep - you can use a wedge on some alt/az mounts - I have one for the CPC. They take a little setting up though and you have to do a drift alignment for best results - especially if imaging. Large alt/az dobs can also be set up on equatorial mounts with tracking and o/ goto. But I've not seen a wedge for your specific scope - don't think one exists to be honest - so it would have to be a diy project Link to comment Share on other sites More sharing options...
catman161 Posted March 17, 2013 Share Posted March 17, 2013 NEQ6 James, go on Link to comment Share on other sites More sharing options...
dawson Posted March 17, 2013 Author Share Posted March 17, 2013 Lol @ Felix Can you imagine how silly my 127mm Mak would look like on an NEQ6! Link to comment Share on other sites More sharing options...
Guest Ely Ellis Posted March 17, 2013 Share Posted March 17, 2013 Before I bought my scope, I was looking at some of the SCT's and one of the selling points for (I think) the 6" SCT, was that the Goto mount had a built-in wedge which would allow it to track like an EQ mount. I suppose a quick and dirty check would be to lower the back two legs of the tripod (assuming the front leg is North), so that the scope points about 53deg up. Obviously don't expect fantastic results, but it would give a basic EQ tracking. The thing with AZ/EL tracking is field rotation. No matter how spot on your tracking is, the image will rotate and therefore give you elongated stars rotating around the centre. This will obviously be more pronounced the longer the exposure. Not sure how to explain, but will have a go. On an EQ mount, lets say you point East, if you put a mark on the top of your scope, then track on EQ to the West, that mark would now be on the underside of the scope as the whole of the sky moves. So, in the East you had two stars, a big one and a little one above it. When it gets to the West, the little one will be below, but in relation to your scope / camera, it would still be in the same position. On an AZ/EL mount, do the same, but the mark would remain on the top of your scope no matter where you started or ended up, the top is the top, so any image would have appeared to rotate. With your two stars, if you took a 12 exposure, the little top star would rotate around the big star to the bottom position. Ah, clear as mud. Does that make any sense? My head hurts now... doh! Ok, now time for the experts to jump in and tell me I'm talking out the other end of my scope. Cheers Martin Link to comment Share on other sites More sharing options...
dawson Posted March 17, 2013 Author Share Posted March 17, 2013 Thanks martin. That's a good explanarion. If there is an abundance of clear nights i'm going to have a go at the tripod leg thing, but no idea how i'll then 2 star align the scope or if i'd even need to try. The poor computer inside will be very confused! If i disn't two star align and used the sidereal travking it would probably still use the alt motor which would mean the tracking was completely off. Confusing. I will give it a go for a laugh though. James Link to comment Share on other sites More sharing options...
Guest Ely Ellis Posted March 17, 2013 Share Posted March 17, 2013 I believe that you carry out your two star align as normal. It should make no difference. The align just lets the computer work out where the objects are. Remember, if you were to use the scope from the equator or North Pole (been there... sorry had to mention that), then it would have to it out just the same. It's just so it knows where to point when you ask it to slew to one of the database objects. Link to comment Share on other sites More sharing options...
Brantuk Posted March 17, 2013 Share Posted March 17, 2013 Be careful the mount doesn't overbalance and fall. Link to comment Share on other sites More sharing options...
Guest Ely Ellis Posted March 17, 2013 Share Posted March 17, 2013 I suppose a 53 degree up angle may be a bit steep for adjusting the legs..... should have though about that Kim. Link to comment Share on other sites More sharing options...
+Graham Posted March 17, 2013 Share Posted March 17, 2013 Building a wedge that sits between your tripod and the mount is a simple project James. If you want post up details of your tripod's top ie the mount attachment points. I can soon do you a set of drawings and instructions of how to build it. Link to comment Share on other sites More sharing options...
dawson Posted March 17, 2013 Author Share Posted March 17, 2013 Graham, I know your motto! Don't spend any time on this, as I agree with the others that I think the wedged mount (if it were possible) would make the whole set up unstable, as the OTA and camera would be leaning the same way it were wedged. The arm which holds the OTA just screws into a cup at the top of the tripod, with a single screw in the centre; some lugs at the bottom of the arm I assume sit next to ridges in the base cup to prevent rotation of the arm in the cup. I think it would be easier to just get an equatorial mount and new OTA Link to comment Share on other sites More sharing options...
+Graham Posted March 17, 2013 Share Posted March 17, 2013 (edited) James Do not worry about the stability. I have made wedges for 12 inch Meade's. The idea is to off set the wedge so the center of gravity stays over the center of the tripod. This way it remains stable. The photos are great. Can you do one more with the tape of the center of the mount base as that cup looks like it has tapered sides. Edited March 17, 2013 by Graham Link to comment Share on other sites More sharing options...
dawson Posted March 17, 2013 Author Share Posted March 17, 2013 Graham, Honestly, I am probably going to get an equatorial mount in the next 12 months, so PLEASE PLEASE do not spend more than 5 minutes on this! I'm sorry it's not well focused, the fixed 50mm lens is on and it was hard to get the subject far enough away to be in focus; hopefully you get the idea it is about 10.75cm at the narrowest part of the taper. James Link to comment Share on other sites More sharing options...
+Graham Posted March 17, 2013 Share Posted March 17, 2013 That will do nicely James. Don't fret about my time it is what I do for fun on cloudy nights. Click on my avitar James and have a look at my gallery and web site. Link to comment Share on other sites More sharing options...
dawson Posted March 17, 2013 Author Share Posted March 17, 2013 I've seen! Plus Ron told me about you. That's why i'm worried you'll spend time on this and design something amazing! I should never have posted pictures. James Link to comment Share on other sites More sharing options...
+Graham Posted March 17, 2013 Share Posted March 17, 2013 Aw come on James if you hadn't I would have nothing to do as this bloody cloud seems to be a perminant fixture. :lol: Link to comment Share on other sites More sharing options...
Guest ollypenrice Posted March 17, 2013 Share Posted March 17, 2013 This is quite complicated. If your alt az mount has software which can be asked to track in RA only then you can use a wedge. If not it can't. Dob equatorial platforms are not set at the equatorial angle. If they were, the scope would fall off the platform anywhere south of Spitzbergen!! They are very clever and perform a conjuring trick instead, using a rolling motion. They don't work like a fork and wedge at all. If you are aimng to do long exposures my advice would (sorry!) be don't! Olly Link to comment Share on other sites More sharing options...
dawson Posted March 17, 2013 Author Share Posted March 17, 2013 Olly is right. I can't see it working. There are no options to tell it that the mount is wedged. And if it were wedged at 52 degrees, the acope cannot physically then get to much below 20 degrees above the horizon as the ota hits the plastic of the mount. Graham, don't do it. James Link to comment Share on other sites More sharing options...
Guest AstroOlly Posted March 20, 2013 Share Posted March 20, 2013 (edited) Here is my attempt at my homemade wedge, check it out at bottom of page http://www.ollyspages.co.uk/p/diy-equipment.html Olly Edited March 20, 2013 by AstroOlly Link to comment Share on other sites More sharing options...
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