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Beginners with an equatorial mount


brianpr1

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After getting plenty of help and advice in the equipment section, I got all the equipment together last Friday and spent the next few days working through the instructions while in front of it. The setup is a second hand Explorer 150p on a loaned Vixen Super Polaris mount. My granddaughter and I have a challenge on our hands to match up to this setup. Reading the instructions without the hardware left a lot of uncertainties, but putting instructions and hardware together, with a lot of headscratching, eventually made sense.

In the continuing foul weather of the last few days I set it up indoors and just played. The Skywatcher instructions suggest that approximate collimation is possible without any added hardware, although they do recommend a collimation cap, so I worked through Astro Baby's tutorial slowly and exactly as instructed, with some anxiety about poking sheets of paper down the tube and the proviso that I would not touch the secondary adjusters unless the secondary was a long way out. It wasn't, so that pleasure is still to come. Even with a bare eyeball centred as best I could, I could relate the picture to the instructions and tweaked the primary into slightly better alignment. I was a bit worried at disturbing the primary, but in the end it was surprisingly easy.

Last job for the telescope was to align the finder. The assembly instructions say to fit the silicon ring (as a fulcrum for the adjusters), but I remembered reading somewhere on SGL that used scopes usually don't have the ring. Ours didn't, so I used an elastic band. It should be a closer fit in the holder but the finder remains in alignment so far.

Then the mount. Before I collected it I downloaded the instructions and read them over and over, but without the hardware that scheme has limitations. I had used Stellarium to get my head around equatorial coords, the instructions for using the vernier scales were clear enough, but the polarscope was a bit of a mystery. That had to wait until I had it in front of me. Once I could see what Vixen and Astro Baby meant by the polarscope index mark, the longitude adjustment etc. it all came together. In continuous overcast and heavy rain showers, without Polaris I had to go as far as I could indoors, so, with longitude scale at roughly 2.7 deg W I set up a few arbitrary times and dates with Stellarium set to the same, and checked that Polaris was, as nearly as I could judge, 180deg around between scope reticule and a zoomed in Stellarium. I think it is probably set up OK. After that there was not much else to do but wait for it to stop raining.

Last night was fairly clear, although I think there must have been a layer of high cloud: Not a lot of stars, and many of them were twinkling. With the polarscope covers on, I tried a rough and ready polar alignment with latitude scale set at 53deg N and sighting along the side of the mount to adjust azimuth towards Polaris. Then I took a look through the polarscope to check it, and Polaris was actually in the FoV, so I think that rough and ready method will do for a quick setup. This is when I felt the need for a red torch, I got Polaris roughly centred, but there was no way to see the engraving in the scope to get more precise alignment.  I know I don't need to be more precise, but with all these bells and whistles available I like to know how to use them. Also the mount has fairly large setting circles with vernier scales and I want to give them a fair trial. They can only be as accurate as the polar alignment.

Next, I wanted to play at tracking, so I swung it around to Vega and centred it. I had to rotate the tube in the rings to get eyepiece and finder accessible, then rebalance, but this was quick and easy and I would not rate it as a problem. I found that focussing was easier and more precise than I expected. I felt that I had taken a risk in choosing to get an equatorial in spite of all the recommendations for a Dobson, and tracking was one of the decision factors. Would it really be as easy as I believed it should be? The answer, for me, is yes it would. I was using a 25mm ep (30X) so I had plenty of time, but it was just a matter of moving the RA wheel now and again. I took time out to ring May and when I got back Vega had moved out of the FoV, but a gentle turn of the wheel brought it back with no perceptible change in declination.

When May arrived we decided to try to find the ring nebula. The mount instructions describe how to find it using the setting circles, but with no red light that was out. We tried star-hopping and I think we were in the right place, but the stars either side were faint and twinkling and we decided it wasn't even worth changing the eyepiece. By this time the moon was high and bright, so we each had a good stare at that and were impressed with the clarity and detail, even at 30X, then the dew came down, all the metal parts were dripping wet and the optics were misting over, so we quit.

I'm sorry to rabbit on at such length, but this was our first time outside with a real telescope, and I feel very pleased that everything worked so well. A bit of prior preparation paid off, the mount was easy to set up and tracking with it was a pleasure. For us, I feel that going for an equatorial was the right decision, and we found it easy to use both scope and mount. Now I'm putting together a shopping list for the wanna-be Astronomer. Insulated and waterproof boots, thermal socks, mittens, a red light, possibly a planisphere and with advice, perhaps a Cheshire/sight tube. With warm feet, the next clear night should be even better.

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Hi to you. Lots of things that could be said to help, however, perhaps I’ll try with this -

For basic observing, you don’t need to fuss with an accurate polar alignment, near enough is fine. Having adjusted the latitude on the mount to 51/52 degrees (you only need to do this once) just point the polar axis north as best you can. This is good enough to get you going and is a whole lot easier than squinting through a polar scope to line up precisely. You then can track your object with just the right ascension control, with the occasional tweak on the declination.

Many of us find that a red dot finder or a Telrad is a great help in aiming the scope at your chosen area of sky. More money I know, but a very worthwhile investment. I’ve never used celestial coordinates, RA & Dec, and much prefer to star hop, works for me and lots of others. However, the trick is to find what works for you, not me or anyone else !

Hopefully others will chime in with more to help.

Good luck from Ed.

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Wise words. Polar scopes have bad eye relief and require the suppleness of a contortionist I found. Better to spend the money of a polar scope on as wide a field, low mag eyepiece that gives a good exit pupil. 

Then align RA ant Dec at linear right angle to each other and lock them. Then slew the mount round on its base in azimuth in line of Polaris, and tilt it up for altitude until Polaris is in centre of your eye piece's field of view.

Having done that lock the mount base and tilt, then release RA ant Dec, which can then be used.

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Hi brianpr1 and welcome to SGL. :hello2:

Glad you are enjoying this wonderful hobby and enjoyed reading you post.

1 hour ago, brianpr1 said:

Last job for the telescope was to align the finder. The assembly instructions say to fit the silicon ring (as a fulcrum for the adjusters), but I remembered reading somewhere on SGL that used scopes usually don't have the ring. Ours didn't, so I used an elastic band. It should be a closer fit in the holder but the finder remains in alignment so far.

You may be able to pick up a small silicone ring from your local hardware shop. I purchased one for use on my ETX105. I just said to the shop assistant: "Do you sell small silicon 'O' rings?" - they had a box under the counter with every size you could imagine. It was the best 0.20p that I spent on my 'scope when I found the size that I required. 

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It's always a pleasure to hear a newcomer getting to grips with new kit. 

You did exactly the right thing in having a play indoors where you could see what you were doing, being familiar with the kit pays big dividends when out in the dark.

Our member @Moonshane has written an excellent guide to star hopping and uses the Ring as his example, you might want to have a look:- https://stargazerslounge.com/topic/197640-collimation-and-star-hopping/

HTH and good luck.

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Often people build a small battery and LED thing to illuminate the polar scope, think you may be able to buy one. Check Astro Baby's site as I have the idea she describes one. But it will likely end up as a DIY job.

For initial visual you "just" need to place Polaris in the centre (easier) or at least in the circle. Eventually you will give better accuracy a go by placing Polaris at the defined position on the circle.

Collimation Cap: Have a look at the Astroboot site, they sell "Posh Plugs", nice anodised plugs for 1.25" focusers to keep crud out. One advantage is that all the 1.25" ones I have also have a 1 to 2 mm hole drilled centrally through them. There is usually an AE sticker over the eyeball end, just take that off. And then you have a very nice collimation cap. My one concern is all the ones I have have a hole but I bought mine 4 to 5 years ago and there is therefore the chance they have changed. The 2" one I have doe not have a hole.

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  • 2 weeks later...

Thanks for the comments and advice. I had no luck with the silicon ring; £1.49 for an assortment, the ones that fitted around the finder were too thick to fit the holder. Plan B works - two elastic bands rather than one. Thanks also for the reference to Moonshane's articles, both very helpful. I also planned to line up next time by ignoring the polarscope and using the main tube instead, but it didn't work out last night.

The first session was Nov 29th. After weeks of overcast and rain and waiting patiently for the clouds to part I had written off last night too, but a final check at almost midnight showed clear sky to the South and overhead. The plan for session 2 was to line up on Polaris, then Vega -> Sheliak -> ring nebula, then via Cygnus to Alpheratz, Mirach and the Andromeda galaxy, but they were all hidden by cloud or below the horizon. I recognized Orion from Stellarium's constellation lines, and it looked bright and clear, so I decided to wing it with no preparation or good knowledge of what to look at.

Polaris and the Northern stars were behind cloud, so I chose the rough alignment: Point about N and rely on the preset latitude, tripod legs retracted, no nonsense about levelling. It would be slower than a Dob because I had to put the weights and the tube on, but it was fairly quick to set up. Then it was a case of swinging it around on to Orion. I did not know what I should be looking at, but I recognized Betelgeuse, the belt and the sword. I managed to home in on Betelgeuse with a combination of sighting alongside the tube, homing in with the finder, then  the 25mm ep. That allowed me to realign the finder, which had previously been out of its holder. Then I tried the star test for collimation that I had read about. It looked OK, with an Airy disc and the diffraction rings looking circular all the way either side of focus. (I bought a collimation tube and rechecked the collimation a few days ago).

Because I didn't know what to look at I decided to settle for finding the Orion nebula, take a general look at Orion then shift to the Pleiades, which were visible as a big smudge way over along the line of the belt. When I shifted to the belt I realized I had a lot to learn. For someone completely inexperienced the different orientations between the real universe, the finder and the ep take a lot of getting used to. Eventually, with lots of trial and error and frequent movements in the wrong direction, I got the three stars of the belt visible in the finder and slowly tracked down the sword using the slomo knobs until I found a fairly big smudge with three bright stars in the centre, which I think must have been the nebula. After that I wandered around concentrating on getting used to the change between finder and ep and trying to get used to the movements needed. The rough alignment worked well enough. Several times I allowed a target to drift outside both ep and finder and brought it back easily with movement in RA alone.

By the time I got to the Pleiades the clouds were beginning to close in and the cold metal felt damp, so I had a good look then packed up- about 90minutes outside and long after my bedtime. This morning I woke to find everything covered in snow. After some reading today I think I missed about 90% of what I could have seen, but there's always next time, and I got some good practice in just handling the equipment and getting a feel for the orientations. Even finding the control knobs and axis locks in the dark needs practice.

EDIT: Am I making problems for myself that don't exist? Somehow I have got the idea that the image in the finder is different to the image in the ep, one being inverted and the other inverted and mirrored. If that is not true then that could be why I find it difficult to make sense of what I'm looking at and have trouble moving the controls the right way. The more I try to work it out the more I think the view in the ep must be the same as in the finder. I will have to wait until tomorrow to check it out.

Another edit: A search on google confirms both images are inverted but not mirrored. My problem has been failing to allow for standing at different positions at the ep. The ep star pattern appears to rotate as I rotate around the ep so I see a mismatch between ep and finder. It's obvious to those who know what they are doing, but as yet I don't.

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On 12/9/2017 at 15:53, brianpr1 said:

Another edit: A search on google confirms both images are inverted but not mirrored. My problem has been failing to allow for standing at different positions at the ep. The ep star pattern appears to rotate as I rotate around the ep so I see a mismatch between ep and finder. It's obvious to those who know what they are doing, but as yet I don't.

Welcome to the joys of visual on an EQ mount!

 

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On 09/12/2017 at 15:53, brianpr1 said:

Another edit: A search on google confirms both images are inverted but not mirrored.

A straight through finder will be inverted, same as the scope. You are right about the orientation shifting depending upon your position relative to the eyepiece.

One purchase worth considering is aTelrad Finder. This, if you are not familiar with it, is a unity gain Finder which projects three circles against the sky, 0.5, 2 and 4 degrees. This makes navigating the scope to the correct position much more simple. It can be used alongside an optical finder too asthis will allow you to refine the position even further.

https://www.firstlightoptics.com/finders/telrad-finder-astronomy.html

It sounds like you are doing an excellent job as it is, and are well on your way to mastering the EQ mount.

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Wise words Stu ! I've never found anything with a finderscope, any red dot finder or Telrad is much easier to use. There are also free Telrad maps available for downloading, these can be printed out and make a great start to observing ,

Nick.

http://www.astro-tom.com/messier/messier_finder_charts/messier_maps.htm

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Well done Brianpr1, learning to use an EQ mount when someone shows you is good but to work it out yourself is impressive and it will stick in your mind quicker. I'm sure you will master observing faster than most, and this site is great for the tweaks that you will come across when you get more into the hobby. Good luck and clear skies.

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  • 1 month later...

Any updates Brian?  The problem with finding things is the combination field inversion combined with the equatorial axis shift.   However, an equatorial mount is just an alt az mount on a 50 degree slope!  If you can adopt this mindset, with a bit of practice things start to fall into place.  Turn Left at Orion is a great book for developing your star hopping finding skills.  I would also recommend either a red dot finder or it's more sophisticated big brother a Telrad.   I once tried to help someone through the procedure of using the polar scope 

 It's harder to describe it than to use it!

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  • 4 weeks later...

Hi Martin,
Thanks for the info, especially re the polar scope.  Apologies for not seeing your post sooner. I agree about treating an eq. as an alt-az set at a crazy angle.
The reason I have taken so long to check SGL is that I have nothing much to report other than frustration at almost continual cloud and rain, frequent sub-zero temperatures and high humidity.
Since the beginning of December I had used the telescope just once, and that was  with a forecast of thick cloud. On my way to bed I noticed that the cloud had cleared and the "supermoon" was shining brightly through the patio door. Rather than waste time getting into multiple layers of warm clothing I chose to break with advice and set up inside the door. It was a case of grab'n go, no pretence of alignment, I just aimed it like a gun then used the slow motions to wander over the surface at 75x. I got about 20min before the cloud rolled back. It was worth it even through double glazing, and at least I had no worries about the optics fogging over.
Last night looked fairly clear, so I set up and had a look. Visibility was fairly poor; according to Stellarium the Andromeda galaxy should have been in a good position but with naked eye I could make out Mirach but not the stars leading to the galaxy, and no trace of the galaxy itself. I decided to aim at Mirach and then track across to see if I could make it out in the 9x50 finder. That was the first surprise, I spent about 20min trying to get Mirach in the finder and still failed to see it positively. I could see plenty of stars but which, if any, was Mirach? I think this is a case where a red dot finder would have saved a lot of time and uncertainty. Eventually I gave up and moved around to Orion, which seemed to be much brighter and clearer than the view to the West. I had been here before on one of the first outings in December but I had another look at the nebula anyway. I managed about an hour in total before cloud rolled in and put a stop to it.
I'm not sure why, but I found it more difficult this time to locate features in the finder. I will experiment a bit with the height of the tripod to get a better angle through the finder.

This all started as a surprise christmas present for my granddaughter. All the technical discussions about equ. vs dob came to nothing when her mother looked at the tripod and mount and refused to tolerate anything so big and clumsy. The only acceptable choice became a Heritage 130p with collapsible tube and dob. mount. Before I can make any useful decisions about my own setup I need to try out both a red dot finder and a dob mount, so I plan to try the Heritage  when I can get my hands on it. Father Christmas also delivered a copy of "Turn left at Orion", and a planisphere too.

Now for feedback on the Vixen mount. So far I have not used the power tracking. I have enough problems without having a power supply and cables to trip over in the dark and I cannot risk damaging them. I found in my spares box two electrical potentiometer knobs of exactly the size for the slow motion shafts, so the motor clutches remain slack and I use the knobs for manual control. I find them very useful for precise tracking and would not give them up without a compelling reason. The whole assembly is big, unwieldy and very heavy, but it is easy to move and set up as four units; tripod, mount, weights and OTA. In my limited experience the time to set up the whole thing is not a problem, it is much less than the time it takes to put on multiple layers of warm clothing. For visual observing it is simple to set up. I know where North is in relation to the house and garden, all I do is place the N leg of the tripod pointing roughly North, the latitude is already set and locked and the job is done.

 

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Not sure if it has been mentioned but you can use a third ring, some use a wooden ring to do with sewing (sorry not sure what they are called) to attach on the scope above the top ring. You can then undo the main rings, rotate the scope as needed and then tighten back up. The new third ring stops the scope from slipping down and save having to re-balance.

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Thanks for the tip on the wooden ring, I will see what my wife knows about them.

After the fiasco of seeing Mirach but not being able to get it in the finder, I set up in desperation last night. Poor visibility and about 80% cloud cover moving fast. I tried a sort of celestial shooting gallery: wait for a star to pop into view then try to get it in the finder before the cloud covered it again. It would obviously involve a lot more waiting than viewing, so I set up inside, viewing through the double glazed door, sat on a kitchen chair and waited.  Eventually, after a few attempts when the cloud covered the target before I homed in on it, a star came into view in quite a big gap to the West and I tried using the eq mount as I assume you would with a dob, just pushing it around and using the tube as a sighting aid. By sighting alternately along the top and then the side of the tube I got it in the finder, then it was easy to lock the axes and line it up with the slow motions.This is real raw beginner's stuff, everyone else seems to just get on with it with no problems. It really is down to my lack of experience, but perhaps the 9x50 finder's fov makes it more difficult than with a lower power finder.

While I had a star lined up and no other targets in sight I tried a quick check of the tracking. Polar alignment was no more than putting the mount roughly North, no attempt at fine tuning, but when I put the star at one edge of the finder I could move it over to the other edge on RA alone without any serious change in declination. The finder's fov is about 5deg so that is about 20 min of RA without needing adjustment in declination, good enough for me.

Before I commit to spending on an RDF I want to get more practice with the gunsight idea, and also borrow my granddaughter's Heritage 130p which has an RDF as standard.

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Last night the cloud dissipated shortly after dark, but still slightly hazy and the usual murk around the horizon. Almost all the sky was clear of cloud, so I got a good view of the constellations.
I decided to set up and have another try at Andromeda. Polaris was not visible so I set up roughly North. Later on Polaris came into view and the tripod was around 15deg out of alignment, but it did not cause any problems in tracking manually.
This time Cassiopea was clear so I used it as a pointer to get a positive ID on Alpheratz and that confirmed the position of Mirach too. The lower part of the square of Pegasus was lost in the murk.
The two hopping stars to the right of Mirach were invisible to my unaided eyes for most of the time, although I thought, or imagined, that now and again I caught a faint twinkle from one or the other. This time I did not even try to use the slow motions, I treated the mount as a sloping dobson, sighted alternately along top and side of the main tube and pushed and shoved it into position. After several minutes of trial and error I got a brighter star than the others into the finder's fov, the tube was pointing at Mirach, that had to be it.
From there it was just as I had practiced in Stellarium, where I have my finder (mag 9x, fov 5.0deg) set up in ocular view. I pushed Mirach to the edge of the finder, knowing that the bright star that came into view at the other edge was uAnd, then pushed that to the edge until vAnd came into view, again brighter than the surrounding stars. At that point I locked the axes and used the slow motions to centre vAnd and looked where Stellarium shows the galaxy. Even in the 9x50 I could see a faint fuzzy blob right where it should be.
After that all I had to do was centre the galaxy and look through the ep. I started with the standard 25mm then after a while I tried the 9mm Celestron Plossl, then the 32mm from the kit I have on loan. Apart from the size I could not see any real difference in the fuzzy images of the galaxy, but the 32mm seemed to give a sharper view of the adjacent stars. As yet I don't know what I should be looking for in eyepieces and I think all views were limited by the hazy conditions. I gave up any hope of seeing M32 or M110.
Even though the mount was misaligned, tracking was easy. I had to make some small adjustments in declination, but that was in more than 40min of tracking after I first centred the galaxy. Even with the 9mm ep I had no problem in manually tracking in RA and I could take my time changing eyepieces and adjusting the focus without fear of losing the target.
I think this was my 6th session with the telescope, but the previous ones have been spent fumbling around learning the basics of the equipment or looking at big easy targets already visible to the naked eye. This is the first time I have found something that was not visible without the telescope and it definitely makes all the effort worth while.

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You seem to be doing very well with your  present setup, well done, and  your already  well on your way, trying help others, new to astronomy.

My first scope had a GEM (German Equatorial Mount). Pretty straight forward to use and operate, once you understand how to setup and operate the mount, but the constant fiddling with the controls and tube rotations was just annoying and time consuming. There had to be something better? There was, the same scope in my signature.

Even your scope, the 150  would have bettered my Celestron 127EQ, but for visual only observations, my choice is to stick with the simplicity and ease of use that a Dobsonian mounted Newtonian telescope provides.

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