Newbie! Celestron Astromaster 130EQ starfinder and DEC setting circle

[alnab01]

Hi everyone

I am a complete novice and was given the above scope as a gift. I am really keen to begin observations but want to familiarise myself with the scope as much as possible. I have a few questions that I hope you can shed some light on for me:

I have had real problems aligning the star-finder with the main scope - to the point where I have had to take a step back because I wasn't getting anywhere with it. I have read reviews and many point to this star-finder as being a major downside of the scope and pretty much useless. Is there a replacement suitable that can be attached?

I have also read on various articles that often, the setting circles on these mounts are not entirely accurate. Nonetheless, I would like to learn how to master them for my own sake. I am having problems understanding the Dec circle as it has 0-90 marked on it several times. Right now it is set to a DEC of 90 with a 0 above and below it on the circle. The best way I can describe what I see is like a clock where 90 sits where the 3 and 9 are and 0 sits where the 12 and 6 are. It reads 90 (3 on clock) when facing north. If I was going west would I move towards 12 o’clock and east would be 6 o’clock? I found that if I pass these then the scope starts pointing at the ground so not sure how to look at objects past these points I do not know which set of numbers I should be using when inputting a given declination. Can someone please explain this to me?

I have SkyX software that came with the scope. My question is when facing south on the screen, it shows me a range of objects. Right now for example, I have clicked Sirius and it has an RA of 06h 45min 53s and DEC of -16'44'12''. How would you input this DEC when it has a negative number? I am clearly doing something wrong as practice in the house has resulted in the scope facing down the way!

I feel a bit silly for asking these questions but am really keen to learn these skills and become really involved in this fascinating hobby/science.

I hope you can offer me some advice.

Many thanks

Alan

[Dave In Vermont]

It shouldn't have any trouble pointing to Sirius - the negative number isn't really below your horizon - and the mount should know that. Pointing straight up with your finger would be pointing to your latitude - around 55°N.

The SkyX, even the low-cost one that came with your scope, is some very good and accurate software. I run it here - though mine is The SkyX Serious edition. But Stellarium is closer to what I have, and I always suggest to people to get it from the website and enjoy it - FREE. Stellarium will also run your telescope if you set it up to do so.

Make sure you have properly entered your exact location in your software-program. If your scope starts aiming at the ground, or something bizarre, this tends to indicate you entered your location wrong.

Keep going - you'll get there!

Dave

[alnab01]

thank you for your response. I dont know if i'm reading the DEC wrong or what ever but my scope was pointing to the ground. I have now downloaded stellarium so will see if this helps. I'll keep playing around with it in the house before taking it out.

Alan

[Ricochet]

I think that your difficulties with the Dec circle probably stem from a misunderstanding of what Dec and RA are,

Consider a simple Alt/Az type mount to start with, like you would get with camera tripod or on a telescope for terrestrial viewing. In this scenario the plane of reference is the ground that you are standing on and you simply have up/down and left/right motions. This is easy to understand and it is obvious that if you want to change the viewing direction from north to south, east or west then you just need to move the telescope using the left/right axis. Where things get difficult is if you point the telescope straight up in the sky, If you want to change from pointing straight up to look west then you first have to move down towards horizontal before you can move left or right. However, if you had this telescope pointing straight up and tried moving it left/right first you would find that it just span around and could come to the conclusion that you should always use the up/down axis to look east or west when in fact you just need to use left/right and not have your telescope pointing straight up in the sky.

An equatorial mount is similar, but more complicated because it is inclined so that its movements are not relative to the ground you are standing on, but to the celestial equator. In this scenario you no longer have up/down and left/right but Dec and RA. Dec is equivalent to up/down and RA is equivalent to left/right. More confusingly, with this new system the north pole is now "up" and the south pole (through the Earth for us in the northern hemisphere) is "down" on the Dec axis while east and west are points on the RA axis. Similarly to the previous example if you want to go from having the telescope pointing north (directly up!) to pointing west then you need to use both the Dec (up/down) and RA (right/left) axis.

The reason that your Dec scale only goes up to 90 is because it is impossible to have an angle "more upwards" than 90 degrees. Whichever way you move the telescope will move it down to 89 degrees and so on. Once you know which 90 corresponds to North then you know that the other 90 corresponds to South and is in fact negative.

Try setting up your telescope and making sure that it is roughly polar aligned. Set the Dec axis to 0 degrees and turn it on the RA axis so that it points towards the southern horizon. Gently move it on each axis and you should be able to see how RA is like left/right and how Dec is like up/down. You should also be able to see that a declination of  0 degrees is at an upwards angle and that is is possible to lower the declination below zero to look at things like Sirius.

I hope this explanation helps, but I'm not sure that I have explained things very well. For now you should just worry about getting the polar alignment approximately right and then play with the scope in order to get to grips with how it moves and track objects across the sky.

[Dave In Vermont]

Hmmm..... Sirius should be up by now for you. Please do keep us informed. I just set my copy of The SkyX for Glasgow, and I show Sirius at +17° from the Horizon. It's up - but barely up. I'd try having it try to find a bright star that would be closer to being straight up to your location at 55N. I'll go take a look.....

Try Capella in Auriga at 46N to your SSW. See where you land.

Dave

[Staffs Oatcake]

The scope you have had was my first scope too. I too found the red dot finder scope more than useless. My first question is have you polar aligned the scope properly and set the scales to 0 at this point? The start position. If it is anything like mine you will find that the metal rings with the markings on were completely in the wrong place. You may need to rotate these to the correct place. Once everything is properly aligned it makes all the readings on the scales easier to understand.

As for that finder scope. I used the skywalk app on my phone and rested it on the main tube to aid alignment and to also guide me to places I wanted to view. Not ideal but far better than that finder.

I also spent a lot of time setting up the scope in daylight to balance the tube and learn about moving the scope around. I found the two videos on the subject extreme useful.

http://youtu.be/

[Flyingfuzz]

With red dot finders (RDF) you must look from the back of the scope along the tube, if not its possible to get a refracted dot which makes the alignment wrong.

Take the finder off the scope in a dark place and holding it at arms length look through it, you will soon find out it has a sweet spot for looking through, they work very well when you are use them correctly .

An optical finder scope inverts the stars and make moving the scope a challenge to start with.

Stick with the RDF if you can and always look along the tube with both eyes open and through the RDF. Don't put your eye up close to the RDF.

[alnab01]

When i polar align with polaris should the dec and ra circles read 0? I thought the dec shoild be 89/90

Alan

[goose35]

The key is once you have the 2 dots on the ref aligned you then have to have your eye positioned in the same place each time you use it.

I had this scope last year too and had the same issue.

Once I got it aligned I put a piece of t tape on the rear half of thtube with a line to help consistently position my eye.

[goose35]

As for the setting circles well they are not the best either.

Bear in mind you have a decent ota which is probably about 70% of the value of the outfit so doesn't leave much for the mount

So it's built down to a price and is bottom of the range.

There are some quite expensive mounts with poor setting circles.

Best advice I can give once you have set up is learn to star hop using a star map or app.

Please don't take this as a negative. This was my first scope last year and I learnt and saw a lot with it. I'll never get rid of it.

[Alan64]

Hello Alan, and welcome,

A 130mm f/5 telescope is quite versatile, and pleasantly bright.  With its 650mm focal-length combined with a range of eyepieces, the gamut may be observed: wider fields-of-view for scanning the Milky Way in the summer, and observing the galaxy in Andromeda and the Pleiades in the winter; and with the aid of a good 2x barlow: the Moon and the planets, Saturn and Jupiter especially, along with the higher magnifications of globular clusters, the smaller galaxies, and planetary nebulae.

Regarding the finder, would you be up to putting another more-useful and more-comfortable one in its place, or to the side a bit closer to the focusser?  The original is molded into the plastic cowling, which also includes the focusser.  I could remove it easily, sawing it off flush to the cowling with a jeweller's saw, then smoothing the plastic to the point where one might not know that it had been there in the first place, but you might not want to go to that trouble.  Then there's this solution...

http://images.buzzillions.com/images_customers/02/09/1604469_27647_raw.jpg

...and by simply adding a new finder and base... http://www.rothervalleyoptics.co.uk/baader-sky-surfer-iii-red-dot-finderscope.html

Or, a 32mm Plossl, at a magnification of 20x(650mm ÷ 32mm = 20x), can be used as a finder there in the focusser.  You may want one in any event, and for the lowest magnification and widest field-of-view possible, and for the observational venues and objects described above...

http://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-sp-plossl-eyepieces.html

I have an equatorial mount: a Celestron CG-4.  It's an EQ3-class mount, and one of the smallest on the market...

It has setting circles, too, but I would have to disassemble the mount-head and tweak said assembly to get it to work, for even in the crudest manner.  I had a Parks EQ-2 class equatorial back in the 1990s, similar to your own, and with setting circles as well...

I never used them, however.  But I certainly did enjoy the motor-drive for the RA axis, having observed Venus one morning, from the time it was still dark, about 5:30 AM, until about noon with the sun there in the sky.  When I ended the session, Venus appeared within the eyepiece as a pale sphere, there in the sunlit sky, and with a granular surface, like sandpaper.  I did have to tweak the declination occasionally, manually, but it was no trouble at all.  The RA axis is the axis to motorise...

The Celestron AstroMaster 130EQ comes in an "MD"(motor-driven) version  No mention has been made of a motor-drive, so I'll have to assume, for the moment, that it did not come with one.

One of the other aspects of an equatorial, besides the use of setting circles, is the ability to motorise it, to virtually halt the Earth in its seemingly irresistible rotation, halting time itself it might also seem, and so to track any given object whilst keeping it centered in the eyepiece's field-of-view; motionless, and automatically...

http://www.firstlightoptics.com/all-mounts-motors/motor-drive-celestron-astromaster-geq-93514.html...or this one, for £3 less, but only if it's the same one in fact... http://www.firstlightoptics.com/skywatcher-mounts/ra-economy-motor-drive-for-eq1.html

You don't have to have a clear view of Polaris, the north star, to align the RA axis for tracking.  Simply level the mount, and point the line of said axis to the north with the aid of a compass.  This will be adequate for visual use.

With the RA axis motorised, one might conceivably engage the drive, with an object of interest centered in the eyepiece, then go inside and have supper, then return in an hour and find that the object is still within the eyepiece's field-of-view.  Such will depend on the accuracy of the initial alignment, however.

When considering eyepieces in addition to the ones that came with the kit, keep in mind that any and all that are acquired may also be used with other telescopes that might be had in future, if a keen interest is engendered by the receipt of a fine gift, and then maintained. 

Did a barlow come with the kit?  If not, a 2x barlow will double the magnification of any eyepiece, and double the amount of eyepieces themselves, and therefore can prevent one from having to purchase extra individual oculars.

Alan

[alnab01]

I currently have the scope out in the living room facing north etc. I tried to align the setting circles with Vega - it was pointing almost straight up and again, when i tried to align for a target in the south, it was almost pointing at the ground. I really don't know what im doing wrong here. 
thanks

[Ricochet]

Have you set your latitude correctly? Watch these two videos and make sure that everything is set up and pointing in the right direction.

https://www.youtube.com/watch?v=TdkB5NCnFps

https://www.youtube.com/watch?v=plx6XXDgf2E

If all that is done correctly have you aligned your RA setting circle as described on page 22 of the manual? Note that in order to do this you will have to be outside at night observing stars in the sky. You can't do it from inside your living room.

My advice would be to forget the setting circles. Whenever the weather is clear go outside and learn to recognise the constellations in the sky so that you can locate objects from their positions relative to the constellations. Practice polar aligning your scope, tracking objects across the sky and slewing from one point to another. After you have mastered those you can come back to the setting circles. At that point you can also point your scope at something and compare the numbers on your setting circles to what they should be which will make figuring out what you are doing wrong a lot easier.

[alnab01]

I am tempted to leave out the RA altogether and just work with the DEC to help me as its the RA that seems to be out. I know i need to collaborate it with a star - not had a chance yet due to constant cloud! 

Alan

[Ricochet]

You can't really just work with one, you need both. If you have both RA and Dec then you have a point, if you have only Dec then you have a circle that your object could be at any point on which would explain why your scoe is ending up pointing in odd directions. You can use https://clearoutside.com to look for when the weather might be good, the forecasts are sometimes right!