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Locating objects with an Alt- Azimuth mount

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#1 Gary Esterly

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Posted 23 June 2021 - 07:09 PM

Not sure if this is the right forum for this post, but I have a question in regards to finding objects with an Alt-Azimuth mount. I am familiar with equatorial mounts and how the they use right ascension and declination to locate objects in the night sky, be it a planet, or nebula or a star. But what about an Alt-Azimuth mount that doesn't have a wedge like my Celestron orange tube C8? It has graduated dials as well, but how does that work in locating a given planet or nebula?


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#2 GaryShaw

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Posted 23 June 2021 - 07:39 PM

Good AZ mounts work extremely well for their intended uses which are visual observing and EAA. They generally require a pretty good leveling of the mount and at least a ‘1 Star’ alignment. They, as well as Eq mounts, work great in combination with ‘plate solving’. You might start by googling ‘goto’ az mounts and reading up on how they work. Same with checking out the tons of YouTube videos that explain different types of mounts, how the work, and what their pros/cons are. 
enjoy

Gary


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#3 havasman

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Posted 23 June 2021 - 07:45 PM

Some variation of star hopping will get you there. Starting from a known object and with a good chart and a good finder you work your way across the sky to what you're hoping to see. The only SCT I ever used had a Telrad on top and it worked well. You could use a red dot finder as well. You might want an optical, magnifying finder in addition to the RDF. Lots of folks find the star hop to be the essence of observing.

You can configure your alt/az mount with encoders and a push-to computer such as the Nexus DSC. Then it's a very simple matter of aligning the system, entering the desired object and zeroing the values on the computer display to put your scope on the target. All my alt/az mounts are configured exactly this way.

You can find a group of encoder kits for different alt/az mounts here  -  https://www.astrodev...der kits/name/1


Edited by havasman, 24 June 2021 - 10:14 AM.

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#4 Gary Esterly

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Posted 23 June 2021 - 07:58 PM

Thanks for the info, I have looked at quite a few YouTube videos on the pros and cons of the various mounts, but they generally do not have much to say about locating objects. I know how to polar align an equatorial mount, but have no clue to useing the alt-azimuth dials on my C8 to locate objects. May have to speed up the purchase of a wedge to help.

#5 bips3453

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Posted 23 June 2021 - 09:14 PM

Not sure if this is the right forum for this post, but I have a question in regards to finding objects with an Alt-Azimuth mount. I am familiar with equatorial mounts and how the they use right ascension and declination to locate objects in the night sky, be it a planet, or nebula or a star. But what about an Alt-Azimuth mount that doesn't have a wedge like my Celestron orange tube C8? It has graduated dials as well, but how does that work in locating a given planet or nebula?

That can be done by looking up current Alt-Az co-ordinates of the desired object on one of the night sky apps and move your scope to that location using setting circles. Make sure to point North first as accurately as possible and level your mount. 



#6 BlueMoon

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Posted 23 June 2021 - 09:30 PM

Star-hopping has been the "tried and true" traditional way of locating objects using alt/az mounts for many, many years. Here's a good wikipedia entry on the basics: https://en.wikipedia...ki/Star_hopping

 

The gist of it is simple, you use known objects in the sky, usually bright stars, to find other objects. Simple star charts are really about all you need. On refractors you can use a finder with a large Field of View and low magnification, while on scopes like dobsonians or newts, a "unity" finder like a Telrad (zero magnification) works quite well.

 

Once you get the hang of it, which doesn't take a lot of practice really, setting up an alt/az mount for observing by star-hopping is a quick and simple solution. No polar alignment, no setting circles needed. The sky is your "road map".

For myself, 100% of my observing uses the star-hopping method.

 

Clear skies.


Edited by BlueMoon, 24 June 2021 - 09:56 AM.

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#7 havasman

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Posted 23 June 2021 - 09:54 PM

Here are some really good charts specifically made to work with the Telrad finder. They're classics.  https://cloudbreakop...d-finder-charts

 

Star hopping isn't hard. And it will very certainly help you see the overhead sky better. Alt/az mounts are really easy to use and a good one is very smooth to operate. Those of us that use them think equatorial mounts are awfully complicated for visual observers to put up with.


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#8 vtornado

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Posted 23 June 2021 - 10:27 PM

 If you download sky safari or some other night time sky app to a tablet or phone,

it will show you the altitude and azimuth of any object for your place and local time.

If you use your mount without the wedge and level the mount, not the altitude scale of the mount should match the altitude of the app.

To get azimuth you will have to turn the mount to match some known object, or you can use relative offsets.

 

Instead of using your scopes altitude scale, you can buy a digital angle meter and hold it on the tube.

The advantage is that the scope does not have to be perfectly level. 



#9 luxo II

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Posted 23 June 2021 - 11:16 PM

Thanks for the info, I ... have no clue to useing the alt-azimuth dials on my C8 to locate objects. May have to speed up the purchase of a wedge to help.

OK ... as one who wrote a program to do this when I had a C8, decades ago in the days of programmable calculators:

 

1. When setting up, accurately level the tripod or base the scope is to be placed on, otherwise your altitude readings will be skewed in some parts of the sky.

 

2. Use the dec circle on the arm to measure altitude. It's in degrees, and it should read correctly (ie 0 dec <=> 0 altitude, 90 dec <=> 90 altitude). 

 

3. The RA circle is used to measure azimuth but there are two catches:

 

a) azimuth is measured in the range 0...360 degrees, but the RA circle is graduated in 0...24h. To solve this I wrote a simple app to convert HH:MM to DDD°MM' and vice versa. Could do the same again for iOS, if you need an app. Even better I could make it convert RA and Dec direct to these altaz coords.

 

b) you don't know before hand where true north (0 azimuth) actually is. To solve this:

- consult SkySafari and locate a bright star near the horizon;

- point the scope at this star and centre it in the field of view;

- from SkySafari, consult its current azimuth and convert that to HH:MM.

- rotate the azimuth circle (the RA circle) to the correct reading per above.

 

At this point 0 on the azimuth circle is now pointing due north. If you use a regular observing location, if there is a suitable target or object you can use that as a reference to set the circle each time in future - in my case I used a distance tower.

 

From this point onwards, if you consult SkySafari to find the alt/az coords of an object and set the scope accordingly, this should put the object in the field of view provided you're reasonably quick about it.


Edited by luxo II, 23 June 2021 - 11:28 PM.


#10 Gary Esterly

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Posted 24 June 2021 - 09:03 AM

OK ... as one who wrote a program to do this when I had a C8, decades ago in the days of programmable calculators:

 

1. When setting up, accurately level the tripod or base the scope is to be placed on, otherwise your altitude readings will be skewed in some parts of the sky.

 

2. Use the dec circle on the arm to measure altitude. It's in degrees, and it should read correctly (ie 0 dec <=> 0 altitude, 90 dec <=> 90 altitude). 

 

3. The RA circle is used to measure azimuth but there are two catches:

 

a) azimuth is measured in the range 0...360 degrees, but the RA circle is graduated in 0...24h. To solve this I wrote a simple app to convert HH:MM to DDD°MM' and vice versa. Could do the same again for iOS, if you need an app. Even better I could make it convert RA and Dec direct to these altaz coords.

 

b) you don't know before hand where true north (0 azimuth) actually is. To solve this:

- consult SkySafari and locate a bright star near the horizon;

- point the scope at this star and centre it in the field of view;

- from SkySafari, consult its current azimuth and convert that to HH:MM.

- rotate the azimuth circle (the RA circle) to the correct reading per above.

 

At this point 0 on the azimuth circle is now pointing due north. If you use a regular observing location, if there is a suitable target or object you can use that as a reference to set the circle each time in future - in my case I used a distance tower.

 

From this point onwards, if you consult SkySafari to find the alt/az coords of an object and set the scope accordingly, this should put the object in the field of view provided you're reasonably quick about it.

Thanks for the info, the app idea is interesting, but I am running Android & Linux (Mint 19.3) apps, so not sure that would be worth your while. Thanks to all for your input, I'm getting closer to figuring this out.



#11 GaryShaw

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Posted 24 June 2021 - 09:11 AM

Thanks for the info, I have looked at quite a few YouTube videos on the pros and cons of the various mounts, but they generally do not have much to say about locating objects. I know how to polar align an equatorial mount, but have no clue to useing the alt-azimuth dials on my C8 to locate objects. May have to speed up the purchase of a wedge to help.

Gary

I thought you were asking the question in the context of a ‘goto’ mount rather than a manual mount.  With a goto az Mount all you do is level it, do a 1 star alignment and then do your ‘goto’ to get to the first object. The ‘Goto’s’ are as simple as selecting the object from a vast list of objects on the handset and pressing “enter”. If the object is not on the handset database, just type in the RA and Dec and hit “enter”. 
 

As others seem to imply, you may be looking for the manual version of an AZ mount. I had one a long while back but quickly found that I was more interested in spending my time observing and studying the object rather than ‘hunting’ for it. I admire visual observers with the patience to do that  but we each decide whats most fun for us.

cheers,

Gary



#12 aa6ww

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Posted 24 June 2021 - 10:55 AM

There is much written about using a compass and a digital level on an OTA to get your bearings correct using a manual Alt-Az mount.

A 360 deg simple compass can be used in the Azimuth directions to get your degrees accurate when locating objects in addition to a simple digital compass on your OTA to get your Altitude coordinates accurate. 

 

Ive tried it and it works pretty good. Don't use your phone compass since its clunky and inaccurate. This has worked well for me in finding dim comets not viewable naked eye. You could mount a simple 360 deg compass, the more resolution the better to your mount in addition to a simple digital level. You would have to figure out how to make it work for your mount, but it does work once everything is set up.

I would go to a nearby bright star and check the alt-az coordinates using one of the star programs, and calibrate your mount to those coordinates once you found your target. Then move the mount to the coordinates you are searching for. 

This becomes a simply DIY coordinate system for an Alt-Az mount and its reasonably accurate for helping aid in locating objects with a simple Alt-Az mount.

 

 ...Ralph


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#13 Gary Esterly

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Posted 24 June 2021 - 03:48 PM

Gary

I thought you were asking the question in the context of a ‘goto’ mount rather than a manual mount.  With a goto az Mount all you do is level it, do a 1 star alignment and then do your ‘goto’ to get to the first object. The ‘Goto’s’ are as simple as selecting the object from a vast list of objects on the handset and pressing “enter”. If the object is not on the handset database, just type in the RA and Dec and hit “enter”. 
 

As others seem to imply, you may be looking for the manual version of an AZ mount. I had one a long while back but quickly found that I was more interested in spending my time observing and studying the object rather than ‘hunting’ for it. I admire visual observers with the patience to do that  but we each decide whats most fun for us.

cheers,

Gary

Gary- yes, I am dealing with an old-school Celestron C8 orange tube, circa 1979. It has a clock drive on one axis but that's it. Down the road, I'd like too scrounge a second mount for this scope and experiment with one of the push-to kits available. I do appreciate your input, thanks!
 



#14 davidmcgo

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Posted 24 June 2021 - 07:25 PM

Your old C8 was meant to be tipped over on a wedge to make it an equatorial to use the setting circles and clock drive.

 

Company7 has the manual here:

 

http://www.company7....8manual1971.pdf

 

That said, if the scope base is on a level table the declination circles on the fork arms should show 90 degrees pointed straight up.  To align the RA circle to act as azimuth you will have to aim the scope at Polaris, set the circle to read 0 (approximately), and then do some math since the Ra scale and azimuth scales are backwards from each other.  Each 15 degrees of azimuth will be 1 hour on the scale.  90 degrees is 6h, 180 degrees is 12h, 270 is 18h.

 

You can use a planetarium app to get the current alt and azimuth and get close that way but the accuracy of your leveling of the table and calibrating the circles will affect the results.

 

Dave



#15 Gary Esterly

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Posted 24 June 2021 - 08:20 PM

Your old C8 was meant to be tipped over on a wedge to make it an equatorial to use the setting circles and clock drive.

 

Company7 has the manual here:

 

http://www.company7....8manual1971.pdf

 

That said, if the scope base is on a level table the declination circles on the fork arms should show 90 degrees pointed straight up.  To align the RA circle to act as azimuth you will have to aim the scope at Polaris, set the circle to read 0 (approximately), and then do some math since the Ra scale and azimuth scales are backwards from each other.  Each 15 degrees of azimuth will be 1 hour on the scale.  90 degrees is 6h, 180 degrees is 12h, 270 is 18h.

 

You can use a planetarium app to get the current alt and azimuth and get close that way but the accuracy of your leveling of the table and calibrating the circles will affect the results.

 

Dave

Very helpful Dave thanks and I really appreciate the manual link. I'll get that printed out pronto!



#16 zerogee

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Posted 25 June 2021 - 04:07 PM

Have a look at the SkyHopper web app for your smartphone. Phone based digital setting circles turns your AltAz mount into a push-to mount. It has worked out well for me. 

 

https://www.cloudyni...etting-circles/




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