HaplessWonder

On 21/12/2023 at 22:12, Chandra said:

I'm glad the mount is working fine. It is important that you try to make an adequate alignment before observing, normally it is enough to do it with three bright stars/objects that the same software suggests you, but if it is not enough you can repeat the process again with three different objects. If you get a proper setup, the goto will have greater precision and more precise tracking it will give you. It will help you to ensure that the mount is as level as possible with the horizon. In my case I use an electronic level, since the floors of terraces, balconies, gardens, etc. may be slightly inclined.

I think that in the economical segment of AZ Goto mounts, only the one linked below allows you to move it manually (also without losing its alignment). In any case, like the rest of the motorized azimuthal mounts, it is not really designed to be used manually, but rather through a controller connected to it or by the application on your smartphone. It would be nice if one day they designed a versatile AZ mount that could be used either in manual mode or in GoTo mode as it suited us.

https://www.firstlightoptics.com/computerised-goto-astronomy-mounts/sky-watcher-az-gti-wifi-alt-az-mount-tripod.html

Good luck and clear skies!

I seem to be quite ok with targeting and focusing on objects although I have barely had any clear skies to point it at beyond the moon and Jupiter. An issue I do have is the tracking on the motorised mount. I thought this would mean the scope would track the object in view but it does not. This is after following the setup procedure.
Still to buy the 5mm BST Starguider ED as I want to learn the basics before splashing out any more money.

Clear skies

1 hour ago, Cosmic Geoff said:

Your mount appears to be of the GoTo type, so you should not be trying to move it by hand at all.  All mounts of this type have some backlash in the gearing - it's normal and you cannot adjust it out, but you can compensate for it in the handset settings (see the handbook).  

If you are not satisfied with the degree of wobble, you need to get a better class of mount, which could be disagreeably expensive.  

Quite right about motor v manual!, I thought it would allow me to move the scope without power supply but seems not as with power it moves so precisely. Now I want to focus, literally on what it is I can see, just need the right weather! 

1 hour ago, Mr Spock said:

One from the archives! Skywatcher 250 on an EQ6 from 2010.

 

I have been looking at similar but right now they are outside my budget, I will stick with the mount I have which is much better with the motor than manual. The battery pack was faulty that came with it but I now have it plugged into a portable power station and it works fantastically.

11 hours ago, Chandra said:

It is normal to see Jupiter with these tones, but of course you should be able to clearly differentiate its equatorial belts of a darker tone, and at least glimpse large formations like the GRS when it is transiting near the meridian... Of course, with your telescope it is possible to differentiate more fine details, but they already require good seeing conditions.

The fact that the stars you observe are pulsating precisely indicates inadequate atmospheric conditions, more inadequate the larger the twinkl is. I don't know what magnification you are observing the stars at, but remember that the higher the magnification, the more difficult it is to get proper focus, and therefore sharpened stars. Furthermore, since they are such bright stars (Sirius, Betelgeuse, it would also be applicable to Rigel, Capella, etc.), beyond inadequate seeing, their own flash in the eyepiece optics will make it difficult for you to see them as points. On the other hand, and on nights with very good seeing, with exit pupils of around 1mm (which means around 130x for your telescope) you will be able to see the diffraction pattern of the stars, since you will be moving close to the resolution limit of your telescope, you will not see them, therefore, as points. If you want to make this observation, however, avoid very bright stars, but also dim stars. I believe that the eyepieces provide the bluish chromatic effect that you see in shiny objects. If you see a bluish stripe and a red stripe at the opposite end of the light source, then it may already be due to an atmospheric refraction effect; you are observing the object when it is still too low above the horizon.

As for what you describe about the mount, that is called backlash, it is a type of effect in the form of unwanted movement that is produced by looseness in poorly adjusted or already very worn mounts. It seems to me from the picture you did share that your mount is a GoTo similar to the Star Discovery... Before considering purchasing another mount I think it is worth checking the axles and trying to adjust the crowns, if that is the problem. Maybe someone here can give you some more specific advice on the matter, in my case I have never disassembled and adjusted motorized axles.

I really appreciate the time you take to provide this level of detailed information, there is a heck of a lot to learn. I have a childlike excitement for observing the cosmos and the objects within it, I am awestruck being able to observe with my own eyes, the endless wonder of I am seeing. I am saying this because I came in on that approach and only now is the sobering reality on me that I need to get into the tech side of it! Like everything, the more you put in, the more you get out.

I think I resolved my mount simply by having it plugged into the mains, with the remote I can control the movement with some precision without 'backlash'.

This is a long, road for me and I am excited about it, I see me getting bigger and more capable scopes but for now I will cut my teeth with this one.

On 13/12/2023 at 06:34, Chandra said:

I think the 5mm BST Starguider I told you about in my previous post will give you excellent performance in your setup if atmospheric conditions allow it. If you want to achieve higher magnifications, in a moderate price range you can opt for the 4.5mm TMB Planetary II (144x), the 4mm SW UWA or TMB (162x), or the 3.2mm BST or TMB (203x). Personally I would not look any further for your setup, and the last one basically for Moon and in a good night. So you must consider several aspects:
1. The higher the magnification, the less light the image you view transmits (this happens because what is known as the exit pupil is reduced). This is really not so important when observing bright objects like Jupiter or the Moon.
2. The higher the magnification, the more difficult it is to get a proper focus point for a sharp vision. Double speed focusers help in this sense. The focuser that mounts your tube does not have double speed.
3. The higher the magnification, the greater the optical demands on the eyepieces, which means that to get decent views the more money you have to invest. I think the ones I suggest would fall within an acceptable minimum.
4. The higher the magnification, the more important is the most precise collimation possible. Let's say that observation at low or medium magnification is more tolerant of inaccurate collimation states. Especially for someone with little practice, it can be very difficult to achieve excellent collimation at f/5.
5. As our colleague tells you, the more magnification you are observing, the more magnified the small vibrations of your support will also be. Any small knock on the tube can be very annoying at high magnification, especially if the mount is not capable of attenuating it properly. With your setup, I think this should be highly considered.

Considering these aspects, at least initially I would not worry about observing with your telescope at more than 150x. On the other hand, most of the time it will be the seeing conditions that will limit your observation, and many times not even with large telescopes you can really observe very well at more than 120x.

The use of a Barlow will prevent you from having to use eyepieces with very low focal lengths to achieve high magnifications, and it also generally somewhat improves the sometimes low eye relief of this type of eyepieces. But if you purchase one, you should still ensure that it is of a minimum of optical quality in order to not introduce more aberrations into the system. It's true that nowadays there are Barlows worth around 50 pounds, but, honestly, I don't think you'll need it for your setup.

As for chromatic aberration, rest assured that it is not coming from your tube (mirrors do not generate chromaticism) but from the eyepiece you are using, which should be a Kellner or perhaps a modified achromat, they are very basic eyepieces that usually come with entrey level kits. That does not mean that other better eyepieces do not also provide some CA, but at least in the center of the field it should be practically imperceptible on a reflector.

Fantastic advice, I will look at the 5mm BST Starguider.

I dont mind paying if the results are worth it.

On 12/12/2023 at 11:46, GrumpiusMaximus said:

The exact eyepiece will vary but generally speaking, the shorter the stated focal length of the eyepiece, the greater the magnification, e.g. a 10mm eyepiece will give you twice the magnification of a 20mm.  They don't gather any more light though as that's purely a function of the aperture of the telescope - in effect, a shorter eyepiece just gives you a bigger picture - but the picture is fundamentally the same.

The limiting factor on magnification is a combination of the aperture of the scope but (more likely) the stability of the mount.  You might be best off getting a 2x Barlow lens as they can be had cheaply.  The Celestron 'Omni' model is inexpensive and gives reasonable performance.  Don't always assume that a higher magnification will give you more detail though, sometimes you can get a sharper view at a lower magnification, even if the object is smaller.

What did the scope come with, eyepiece-wise?

A reflector shouldn't be giving you much CA at all.  Can you describe it?  Usually, CA is a purplish fringing around a bright object.

25mm
12mm
10mm
6.3mm
2x Barlow lens
Meade 2x telenegative Amplifier

Not getting much by way of clear sky right now, but last night I glimpsed Jupiter and Sirius, Jupiter appears almost washed out with white light but I see that quite clearly albeit small, it's moons also apparent with reflected sunlight. I doubt I can see much clearer than this. 

Sirius and Betelgeuse, I focus carefully but they never resolve to a crisp point, I mean for what I am using it is maybe the expected result. They appear with a bluish tinge and seem to pulse a little.

A problem I do have is the mount - it just has up and down movement but it appears loose so when I have an aim and let go of the scope it drops so Ill need to look at why that is, maybe another mount.

On 10/12/2023 at 20:01, GrumpiusMaximus said:

Glad this got sorted out.  That 200P was in a very sorry state and somebody with some experience could have brought it around but they were asking silly money for it in that condition.

Good luck with the 130.  What model did you get in the end?

Managed to poke a look through the clouds yesterday and saw the fantastic sight of Jupiter with her gases! Her moons also, superb.

I want to know what the best eyepiece is for observing the planets in their optimum, also I noticed chromatic aberration, is there anything I can do about that? 

On 10/12/2023 at 20:43, Mandy D said:

Actually, it is her. Glad to have been of help and to be appreciated.

My apologies, it's been a very long week.

I want to say a huge thank you to everyone who advised and helped me on this telescope, it has now been returned to the seller.

Particular thanks to @Mandy D for his detailed opinions.

I have a replacement scope, not as large - a 130mm Skywatcher reflector, motorised, it seems to be perfect for what I want.

Thanks once again chaps and wishing you clear skies!

Barry

1 hour ago, Mandy D said:

The bent vane will cause the diffraction spikes on bright stars and the brighter planets to be distorted. On the Moon, it will probably make little difference to be fair. Those pins are roll pins and are made from spring steel. You could probably squeeze it back in with mole grips, but I would want to remove the vane and properly straighten it, first. The other thing the bent vane will have done is to decentralise the secondary mirror, but that can be adjusted back into place using the knurled knobs on the outside of the tube.

I've never used 6SE, so cannot comment on it, but they seem to be regarded as good telescopes. Obviously, it would be best if you posted pics and asked questions in here once you have found one and before you buy. It does have a slightly longer focal length than the 200P, 1500 mm against 1200 mm, which will cause you problems if you want to image the whole of the full Moon with a crop sensor DSLR, but visually with an eyepiece, it will just be a little more difficult to point and provide higher (but dimmer) magnifications than the 200P using the same eyepiece. It's maximum useable magnification will also be lower. Hopefully, you will find what you want.

Im indebted to you for all your help, I am an idiot for jumping in on this telescope believing it a good deal. 

Could you advise on a telescope for a budget of around £500-£600 that will allow me to observe the planets and galaxies, I'd at least like to see the swirling gases on Jupiter or as I said before the poles on Mars.

4 minutes ago, Mandy D said:

Hmm, that vane is distinctly bent. The pin that holds the outer end in the tensioner is also not properly in place. Someone has been messing around with tht scope. The focuser should run smoothly, taking very little effort to turn the knob; it is a friction drive, so no gears in there.

In light of all these problems, I think you are right to seek a refund and return this. It's a shame, as these are generally such good scopes.

I've attached a photo of mine to show how the spider should look. You can clearly see the fixings at the outer ends.

With the vane and pin as it is, does that actually cause an issue? I will now be sending this back but I will be without a telescope, I am now looking at a Celestron NexStar 6SE, it seems to offer everything we wanted.

21 hours ago, Mandy D said:

@HaplessWonder I paid £200 for my 200P second-hand, complete, but no laser, no motorised focuser, but with the standard finderscope. I would say for the OTA on it's own, £245 is too much. I'd want to pay no more than about £150. I guess you had shipping costs as part of your price, whereas I collected.

OK, to get the focuser working there are two things you may have to do. Remove the motor unit. Next, there is locking screw on the focuser barrel, with a knurled knob. You need to loosen that in order for the focuser drawtube to slide in and out. You can see the locking knob to the left in your third photo.

If it is not focusing, make sure you have the extension piece in the focuser, which appears to be shown fitted in the same photo. Then point the scope at a distant object and rack the focuser in and out. If it still does not focus, start pulling the eyepiece out of the focuser. At some point it should focus. If that fails, remove the extension and try without to get the eyepiece closer in. You'll have to hold the eypiece square by hand as the drawtube has a 2" bore. Mine will easily focus on the church clock a quarter mile up the road. If you are getting a blurry image, this is simply going to be down to the closeness of the object and the position the eyepiece needs to be in. It will almost certainly focus at some point.

EDIT: Can you check the spider vane mounting point as indicated by my pink circling? It might be nothing but it looks damaged to me. It should look like the other 3.

Here is a closer shot of that mounting point you highlighted, I asked another forum user above the same, the vane itself is bent as if folded at one time. 

As for the focus puller, should it be so stiff and hard to move? it's like there is grit or rust gripping or catching it inside.

The wheel with the holes which appears to turn a gear that moves the focuser in and out does work with some force but the motorised unit now longer functions even with a new battery.

19 hours ago, John said:

Would it be possible to get a full refund on the scope and return it on the basis of the description being incorrect and the motor focuser not working as claimed ?

The reason that I'm asking is that there are a number of things about the scope that lead me to believe that it might have had a hard life. The secondary vane support point that @Mandy D mentions is one and also the vanes themselves seem bent from the photo looking down the scope tube you posted.

Given that this is an optical tube from the Skywatcher 200P dobsonian that is being sold without the mount, I can't help wondering how the two became separated - an accident of some sort perhaps ?

If you feel you have to keep it then do try and get a hefty discount on that asking price. I would hesitate even at £100 to be honest with you, given the other issues that will need to be sorted out.

About those vanes, I am enclosing clearer pics of the ones Mandy D zeroed in on, to the touch I can feel an actual crimp in that vane as if it has been bent to put a fold in it. What impact does this have?

19 hours ago, NGC 1502 said:

If it were me I’d get a full refund if possible.  Then check out our sponsors First Light Optics (link at the top of the page) and purchase a brand new ready to use 8” Dobsonian. Several brands to choose from.

Thats what Im looking to do, so far the seller has just quoted a 'sold as seen' so will be fun to get this returned now, I am fine as ebay rules for used state that the item is in good working order, which it doesnt appear to be.

20 hours ago, Chandra said:

@mandyd has given you excellent advice and instructions... You really don't need the motorized focuser for visual observation, it is a perfectly dispensable element that can be saved. Many years ago I had a Newton 8" f/6 and I can also tell you that it is a great multipurpose tube for astronomical observation, it is surely the most common aperture among amateurs. Honestly, in my opinion, speaking in terms of optics, there is no a big jump between an 8" and a 10", another thing is the question of price, since the seller labeled one thing but the product was another. 

The finder is a Telrad. I've never used one, but those who have are generally very fond of them. This is one of the types of "0 power finder" (another type would be the red dot finders that most small telescopes now carry, for example). There are several threads here about its use, here I leave the link to one of them so you can decide whether to keep it or return it (if possible). https://stargazerslounge.com/topic/128382-how-good-is-a-telrad-finderscope/

The laser should not be red, but green light, which is the one for astronomical use. Green light is the one that offers the most brightness with the least power and, therefore, danger, which is why it is the type of laser authorized for this use. It is also a useful accessory in locating objects once it is calibrated with the tube's optics.

The focal ratio of f/6 I think will help you get a less complicated collimation practice than your expected f/4.8, that's a plus for you. The larger the focal ratio, the greater the tolerance for decollimation, or inaccuracy in collimation, and more so for visual purposes. This way it is not necessary to "waste" so much time trying to achieve precise optical alignment (which can sometimes be a lot of resistance, especially with optics lower than f/5). https://stargazerslounge.com/topic/50737-skywatcher-8-f6-dobsonian/

As you say, now the important thing is to try to focus on a distant object (as far away as possible from your location) and verify the mechanical condition of the focuser. Then will come the optical review... and the expansion of your range of eyepieces...

Fantastic advice, thanks a lot. I am going to look to return it as there are too many questions I have about it. Which means I am back in the market for a good scope that will get me nice close ups to at least see the poles on Mars, Jupiter's spot and maybe it's clouds and ofc Saturn's rings. If I can push it so I could also observe galaxies that would be the perfect scope for me.

Thanks

Barry

12 minutes ago, Mandy D said:

I would not worry about the motorised focuser, as you don't need it and the same goes for the laser. Avoid the aggro of return shipping and getting your money back if you can by asking for a rebate agains the non-working parts and just send those back if he wants them. But, try new batteries first. It is no good testing batteries by measuring their voltage with a multimeter as that does not load them and they will likely show full voltage regardless.

I think, once you get through the disappointmenet and start fixing it up, you'll be a lot happier. As long as you have not overpaid for this after any rebates, it is worth keeping. |Do you have eyepieces with it? You might have to remove the motorised focuser bit to focus manually, but I'm not sure. It will be very easy if necessary and you have the knob on the other side that you can focus with manually.

Good to see you are not fazed by making the mount.

I have paid £245 for it as is, which right now am thinking it is too much but I will be guided by what you say, if you say this a is a good telescope.

The focuser turns the vertical bar, is that the drive for the gear I assume? anyway, it turns one way but not the other. The bar turns but the actual focus itself does not move with the turning.

So two things there, it only turns one way and the focus itself isnt actually moved.

Eyepieces I own a NEEWER PLOSSL 25MM which I have inserted, I can see blurry images but cannot get anything in focus at all, maybe the objects are too close.

What would be a reasonable price for this telescope? 

6 minutes ago, Mandy D said:

Nope, that is not a 250PX, it is, instead a 200P. Both are fine telescopes and both have the same 1200 mm focal length. I am sorry that you have suffered this problem with your purchase. It seems to have a motorised focuser attachement, a laser pointer and a finder. If you cannot, or do not want to return this for refund, then it is possible to make a really good setup with it. The 200P has an 8 inch mirror, instead of the 10 inch that you wer expecting. It will only gather 64% of the light of the larger instrument, but that is still a lot! I have bothe 200p and 250PX and am disappointed with neither.

You will need to build a Dobsonian base for it, but that is not difficult, especially as you have the azimuth mounts already on the tube. To test it, all you need to do is lay it down on a table and prevent it from rolling, then point it at something, in daylight (not the Sun!) a long way off and see if you can focus it. Don't worry if all you see through the eyepiece is black, that will just mean the collimation is so far out that the eyepiece cannot see the primary mirror. My 200P arrived like that and it took 5 minutes to sort.

I think it is likely that you have a very decent telescope there. I have taken some stunning images of the Moon with mine. We are all here to help you get through these teething problems and build things up to the point where this no longer looks like a problem, but an opportunity. You will certainly learn a lot sorting it, but there really is not a lot to go wrong with these telescopes. Just check the primary mirror by looking down the tube. There should be some dust on it, but it should be highly reflective. Do NOT attempt to clean it in any way at this time! That can come later if necessary.

It was listed as a 250PX and as an addition the seller stated 'I am told it is 8' - maybe I was too hasty and should have checked into it.

So, you say it is a good telescope? It certainly feels it from weight and size alone. But those accessories, the focuser, it has a 9v battery which I have tested and it is a good battery, however none of the buttons do anything at all, I would expect the eyepiece part to move around but nothing.

At this stage I just want to see if all is well with it, if the motorised focuser isnt working itll be a return as he stated it was fully working.

The laser pointer has also good batteries but pushing the button nothing appears when I aim at a wall, expecting a red dot.

I really appreciate your help, me and the wife are so keen to just sit romantically gazing upwards so we just want a good scope that will do this.

Not a problem with the mount as it looks a simple DIY project, it's the basics I need to check work first.

The mirror looks sound, little dust but sound.

6 hours ago, Mandy D said:

If this is a 250PX as you say, then it will have the alt mounting points on the tube, unless they have been removed. In which case, you will see, clearly, where they were, so no problem finding the balance point. I've included a photo of my 200P, which shows the Dobsonian mounting points - the large black bit. The thread in the middle is M10 x 1.5. It is possible that these may have been removed, but you can still mount it using rings, like I have.

Hi Mandy, it's arrived but I have to say I feel somewhat disappointed. Maybe it is my rush to grab it from ebay. Anyway, here are some pics of it and it's features, I am unsure now that this is a 250PX as per the listing as google searches show a different model.

I would like to test it if I can with what I have, there must be some way to. It doesnt have a mount but if I can at least test it to see that it all works.

20 hours ago, John said:

There are lots of other DIY dobsonian telescope plans on the web. Some are so simple even I could make them ! 🙄

My only tip would be to use plywood rather than MDF if possible. Plywood is strong but lighter than MDF. 

Ill have to take a look when the scope gets here, I'm not sure if bearings are needed or where the balance point is etc, I will consider it.

12 hours ago, Mandy D said:

@HaplessWonder There is a great home-made Dobsonian mount built for a 200P by @PeterStudz on this forum. It is a rather unique design as it has cutouts of the Moon and constellations in the uprights and has even been lit with a red lamp in some pictures. Here is a link to one of his pictures of it. He has posted better pictures, but I didn't dig far enough to find them, tonight.

That looks very good indeed, wonder if he would share his plans?

13 hours ago, John said:

I think the minimum that would do the job would be an HEQ5:

Sky-Watcher HEQ5 PRO Go-To Astronomy Mount | First Light Optics

Alternatively, for visual use only, you could consider building a dobsonian mount for the scope as detailed here:

How to build a Dobsonian mount - BBC Sky at Night Magazine

 

 

 

I think this is what I am going to have to do, the DIY route. Have to be a tradesman with my DIY skills.

Thanks for the suggestion.

Hello,

I have just rush bought a Skywatcher 250PX and only after payment have I seen in the description that there is no stand. I am gutted! I am usually so careful with listings and bids. 

I just read the original mount that would come with the telescope arent available separately so what stands or mounts are compatible with this telescope? Me and my partner are enthusiasts so are not wanting to be all flash, we just wanted to gaze at the planets and nearby objects as clearly as possible.

Appreciate any advice.

B.