Some beginner questions

[astromog]

Hi Stargazers,

I bought an AZ Goto scope recently and finally had a clear night last night when I was "free" for a couple of hours. I could do with some help and advice. 

The first question is about finder scope set up. This is the first time I used the scope so got it focused by pointing at the moon, and similarly checked the finder-scope had the moon in view too so I knew they were roughly in line. Then, tried a star. Had great difficulty getting the star centred on both main and finder scope. I found that the two adjustment knobs were changing the position in unpredictable ways, moving the centre of the cross-hairs down down down down, then sideways a bit, then up up up, in a sort of U shape. In the end I settled for the finder scope being a bit off, but knowing that if I positioned the object up and right of the cross-hairs it would then be visible in the main scope. I assume I have perhaps not inserted the finder-scope properly in the mount? What's the right way to do this? (There are three instruction manuals with the telescope but none of them tell you how to set up the finder scope and get it properly adjusted!)

The second question is about finding bright stars. Is there a website, or app that helps you learn them (preferably for PC - I'd rather use a nice large screen than a mobile phone)? The sort of thing I'm thinking of is like the many "learn a new language" web sites and apps that are out there, that teach you a bit then test you a couple of different ways, maybe have some flash cards etc. and before you know it you've learned some cool new stuff. The reason I ask is my scope needs me to point it at stars I know the names of, which are few an far between. Suzanne Vega and the old dog Sirius Black and are the only ones I can think of right now, apart from Polaris, which doesn't really count as it's a missile not a person. Seriously though, I have found a lot of guides to help learn constellations, but not to the bright stars. I would like to learn all the constellations eventually, but right now it's just the brightest stars I need to know. The best guide I have found so far is entirely based around Ursa Major, which I couldn't really see last night - I am surrounded by houses, trees and street lamps (not to mention intermittent clouds even on a clear night) so need to be able to find and name the bright stars with the part of the sky I can see at any time... otherwise I can't really get started as I can't do the setup needed to use the Goto...

The third question is about what location accuracy I can expect from such a scope. I set up the scope by pointing it at Suzanne Vega, then Polaris. When it slewed to Polaris, it was visible in the finder scope but as expected, not centred and not visible in the main scope, so I centred it in finder (to my offset centre see above) and main scope. Having entered this correction, I thought that if I went to some object it would be visible in the main scope. However, each object I went to, I found was out by some way and I kept having to adjust. Is this normal, or again, have I perhaps not set the scope up properly? Any tips appreciated.

You have probably guessed that what ended the evening was actually dew. The fourth and final question I wanted to ask was about dew protection. I have never seen this before, perhaps because my previous scopes have been reflector/refractor, but I wasn't out for that long before there was a thick covering on both finder and main scope. I notice that dew shields and heated dew shields for my scope are not that different in price (~£35 vs ~£55 for astrozap) but I'd rather not have something else drawing power if I can avoid it. I also don't want dew though! Given the fact I'm in a high humidity area, will an unheated dew shield do the business or do I really need heating? Also, what about my finder scope? I was really surprised that dewed up so quick! Finally, what is the deal with the dew controllers? What are they for and what's the difference with the number of channels etc.? In order to make this whole thing work, I really need to keep it simple so that I can leave the scope fully set up and just grab it when I have the chance and put it in the back garden. Having unnecessary extra bits of kit is something I'd like to avoid if possible.

I'm not sure how many of the questions I've asked are generic and how many are scope specific. The scope is a Sky Watcher SkyMax 127 if that helps at all. In regard to situation, I'm in the UK in an urban area, but often only have an hour or two I can grab, and that may be interrupted by things I need to deal with. Already had a reflector that never got used because it takes longer to do anything useful with it than I usually have available (due to Earth turning), so bought the goto scope as something I can use when I have a chance and a clear sky (rare combination) without needing too much time. Was delighted last night after I had a 15 minute interruption, I returned to the scope to find it still showing Mars, which I'd just got centred before the call came in.

Apologies for the long post. Part of the blurb for newbies said to not post multiple posts unnecessarily or you'll be penalised somehow! Thanks in advance for your help and advice.

Astromog

[Mr niall]

Hello there - all great questions, you’ll probably get a few answers!

1. Yes they’re  bit of a faff, you’ll find they actually describe an “X” or more of a Nike swoosh when you adjust them; what is sometimes easier is looking straight ahead with both eyes open and one over the eyepiece of the finder. When the view in the finder and your eyes match then you’re bang on. But yes, you aren’t necessarily doing it wrong. Using the biggest eyepiece you have helps as it gives you a wider field.

2. Yes! Loads, but what I’d recommend most is The book Turn Left At Orion - worth it’s  weight in gold. In terms of apps, Stellarium is by far the best pc package and free! iPad apps include Star Walk 2 and Sky Safari. With many mounts you can actually use sky safari to control your mount. Which mount do you have?

3. Pointing accuracy, mostly depends on initial setup. 3 star alignment is better than 2. And choosing stars that are very far apart is even better; Polaris and vega are quite close so this has a higher chance of introducing errors.  Your Mak has a really narrow field of view anyway so it helps to get the initial setup as accurate as possible to reduce the need to slew to target.

4. Maks are dew magnets! There’s no concensus on heated vs traditional dew shields. I used to use a piece of A3 black sugar paper, worked a treat!. Heated dew shields need a completely separate controller to regulate the voltage eg heat so factor that into the price.

happy hunting.

[RT65CB-SWL]

Hi @astromog and welcome to SGL. 

1. align the finderscope during the day on a TV/radio mast or anything that is 1/2 to 1.0 km/mile away if you can. The further the away, the better. Don't use a tree.
2. Stellarium for PC/Mac- it's free, (you have to pay for the Android/iOS version).
3. as per above reply
4. dew-shield is a must have accessory for any Mak or SCT 'scope. They also require a minimum cool down time of thirty to forty minutes before viewing. 
5. when finished for the night and indoors, re-attach the OTA to the mount, remove the objective end cap and angle it so it is facing down, then any condensation will not leak into the tube. Also remove any end caps from any eyepieces and/or accessories and place in on a dish rack to dry. When all dry put it all away. 

[astromog]

3 hours ago, Mr niall said:

Hello there - all great questions, you’ll probably get a few answers!

1. Yes they’re  bit of a faff, you’ll find they actually describe an “X” or more of a Nike swoosh when you adjust them; what is sometimes easier is looking straight ahead with both eyes open and one over the eyepiece of the finder. When the view in the finder and your eyes match then you’re bang on. But yes, you aren’t necessarily doing it wrong. Using the biggest eyepiece you have helps as it gives you a wider field.

2. Yes! Loads, but what I’d recommend most is The book Turn Left At Orion - worth it’s  weight in gold. In terms of apps, Stellarium is by far the best pc package and free! iPad apps include Star Walk 2 and Sky Safari. With many mounts you can actually use sky safari to control your mount. Which mount do you have?

3. Pointing accuracy, mostly depends on initial setup. 3 star alignment is better than 2. And choosing stars that are very far apart is even better; Polaris and vega are quite close so this has a higher chance of introducing errors.  Your Mak has a really narrow field of view anyway so it helps to get the initial setup as accurate as possible to reduce the need to slew to target.

4. Maks are dew magnets! There’s no concensus on heated vs traditional dew shields. I used to use a piece of A3 black sugar paper, worked a treat!. Heated dew shields need a completely separate controller to regulate the voltage eg heat so factor that into the price.

happy hunting.

Many thanks for the answers.

1. OK good to know that's normal, if a bit dissapointing - the old reflector was a lot cheaper, and has a red dot type finder with straightforward up/down left/right thumb wheels to adjust it with, which crucially you can set up once and then leave. The new finderscope shifts position if you touch it e.g. when replacing the lens caps, which means it needs re-adjusting every time as there is no way to lock it in place once adjusted... however it does allow me to see more stars than the red-dot finder, which is important with all the street lamps around!

2, 3. OK, thanks for the tip ?. I'll try to do three star alignment next time... of course I need to know more stars to do that as Sirius is normally below the horizon. Thanks very much for the book recommendation - people have been asking me for Christmas present ideas, that will do nicely. I'll have a look at Stellarium too! I have the Sky Watcher SynScan AZ GotoMount - is that controllable by sky safari? I saw that the control unit had an input on and a cable to connect to a computer.

4. OK understood. Thanks for the info, I think I'll order an unheated one this evening. Having read a bit more about this, I understand that the problem is that the telescope cools faster than the air around it and that actually part of the reason a dew shield works is the insulating effect, which keeps the scope warm enough to stop the dew forming. I may need to think about that a bit actually as I keep mine in the conservatory so I can quickly get it into the garden if I have a chance, but it's pretty cool in there most of the time (15C right now vs outside temp 13C, dew point 12C). In any case, I don't think my star gazing sessions are long enough to need a heated one, which is a relief as it would mean another power supply, more dangling cables, a controller etc. all of which would make the new scope highly likely to go as unused as the reflector!

Thanks again ?

PS love the Churchill quote - haven't seen that before!

[astromog]

Thanks @Philip R 

[JOC]

My knobs frequently describe a U as I try to set up the finderscope.  I use two one RDF and one optical RACI.  This is because I struggle to find things in the RACI.  The RDF isn't spot on centred - there isn't enough adjustment to get it to exactly where I want it without installing shims and tbh that's just too much faffing.  As you discovered providing you know and can apply difference being slightly off isn't a huge problem - I have the RACI spot on and I know that if I can find something with the RDF it will be in the field of view of the RACI and then if I centre it in the RACI it will be OK in the telescope.  So for that part of the question you might find that observation useful.

[astromog]

@JOC Thanks, much appreciated. I'm finding I'm making a lot of use of the glossary page being new here, and it told me RDF = Red Dot Finder, but I'm not sure what a RACI is? Sounds very useful, so I'm keen to find out!

Thanks

[JOC]

It's Right Angle Correct Image (RACI), it's an optical finder - the straight through ones as supplied with most telescopes are just like a miniature refracting telescopes - the trouble is I found I got a crick in the neck trying to use it on a bigger reflector as you can't stand directly behind them due to the telescope being where you would want to stand.  The Right Angled ones are build with a star diagonal in the end allowing them to be used from the side of the scope.  Sort of reverse periscope logic - you can see around a corner with a diagonal.  The correct Image bit just means that it flips the image up the right way - normally a reflecting telescope turns things upside down, but in the sky that doesn't usually cause too many problems.  However, when you are chasing stuff with a finder the fact that things then move predictably in the finder is probably a help - an internal mirror just flips everything back the right way around.  You just have to remember once back at the telescope that things may move in opposite directions.  So you get Right Angle, RA, Correct Image, CI.   Ta....da.....RACI!  

I hope this helps

PS.  I'm only a beginner too, but I think the above is correct.

[Astro Imp]

I find it strange you tell us tour finder moves when touching it. There appears to be something not quite right here. Is the movement the finder in the mounting or the mount not secure? If the former have you seated the finder in the "O" ring properly, if the latter it would seem the fixing needs tightening. To prevent dew on the finder I always replace the end cap on damp nights.

I'm sure with a little practice you'll get to enjoy your your new toy, good luck and keep us posted.