RayD

They are both very very good mounts within the price range. I find the more modern design of the CEM superb, and the dovetail USB and power distribution is abslutely awesome. However, the nuts and bolts design of the Mesu means that it just works, and works, and works and has done so for a number of years. I love both but, being honest, for different reasons. The CEM is much easier to balance, but the balancing isn't as critical on the Mesu. I agree, if the non EC version will work for you then there is no reason at all to get one with encoders. I haven't tried the non EC so wouldn't comment, and went for the EC purely based on the low PE this model offers. I don't think the PE on the non EC model is massively different, but I had the budget for the EC and thought it couldn't make it worse. I must confess to not being a fan of the Mesu 200e fixings now being studs. I'm not saying it is worse or performs any less well than my model, but it just doesn't sit right to my eye. It's certainly a nice decision to have to make as they are both great mounts, but are actually quite different.

No worries. Yes without doubt, on performance alone, I would have another Mesu all day long. On practical design with through the mount cabling, built in wifi and GPS etc I would have the CEM all day long. They both perform well, but the Mesu is ultra consistent and reliable with its results (and it doesn't use PEC). Ultimately I'd love an ASA, but that isn't going to happen any time soon 😂

A quote below from @andrew s from a post about PEC : "I don't have any experience with your mount but with mine, Paramount ME, I use PEC as it minimises the work the auto quider has to do. In controll enginering terms it is better to remove error before you use a a feedback loop that requires an error to have developed before you can correct it. Regards Andrew" This is exactly what I believe is the reason for the encoder on the RA axis, it automatically reduces the PE without having to run a PEC routine such that the guider has to do very little work, so it makes achieving a lower RMS value easier, albiet achieving it without is probably not an impossibility. If what you are saying is correct then advice like Andrew offered is incorrect and PEC has no place at all if guiding? Not every question can be answered with theory and mathematics. Sometimes you just need to try it and see the results.

That's great. I would much prefer to have a mount that uses modelling, such as the 10Micron etc than guiding. Unfortunately I can't afford one 🙁

I never said it was misplaced. I think it was, and is, perfectly valid. However, I'm not trying to prove you wrong, I simply offered my view on your question of why one would spend extra money for encoders when guiding.

Great story, Stu, and sounds like a really great couple of 'meets.'

Possibly, Andrew. When looking at the guide graph it really doesn't do an awful lot but if imaging at very long FL I suspect you could well be right, and it would then make sense to have it.

Agreed. But I do 20 minute subs so how does that help me? As you rightly show, the EC model with the encoder on the RA axis has an extremely low PE which means there is very little interaction with the guide system, but it is needed. It just means the guiding is incredibly smooth and accurate for a mount of this price. The EC2 model has an encoder on the dec axis also but as you rightly pointed out earlier, this axis moves very little, so there is already little for the guider to do anyway, so I did not see this as a necessary addition. I'm not sure what market iOptron were aiming at with the EC2, but for sure the EC performs exceptionally well with the RA encoder reducing the PE to the level it is at. As I noted, I have managed acceptable 15 minute unguided subs with my Mesu200, but I still guide with that as well. I think iOptron have done it smart making it optional to have none, one or two encoders. If you image wide field and only short subs then the likelihood is the EC will be absolutely fine and perform perfectly well. If you image loger focal length and much longer subs you may want to consider the EC. I'm not sure where the EC2 fits in, but it is an option if it is felt to be necessary. It's a good mount for the money, encoders or not.

The encoder on the EC model is on the RA axis to reduce the PE to a very low level making guiding very easy. What happens to the dec axis if you don't guide?

Yes I have a CEM 120EC and Mesu 200. Neither is necessarily designed for unguided imaging as neither has an alternative option for PA error, atmospheric distortions or cone error, as do the mounts with a pointing model. However, I have run 15 minute unguided test images just for fun on my Mesu with great success, but I do guide. Both are excellent and both guide to 0.3"/p regularly. I'd recommend either but the Mesu, in my opinion, is the better of the 2.

I'd second the RedCat. It's very good value for money and certainly portable.

Yes it is their own internal database which is used to form an accurate pointing model. @Davey-T has one, and they are one wicked looking mount.

That's fine. I would keep eye on ABS as they often come up used, but get snapped up. Yes as you say, late for decent nebulae now, so you may want to ditch the Optolong for the time being as it will remove colour from any galaxies you're imaging, unless you are wanting to add a Ha element. The RedCat is a great little OTA so I doubt any of your issues are related to that.

10Micron doesn't really track open loop. It uses a pointing model which accounts for PA discrepancy and any cone error you may have. It doesn't need guiding but the pointing model is their alternative to it, but the pointing model kind of close loops things.

Is there a specific thing you are looking to achieve from a filter? Is it just light pollution you want to fight, or are you specifically wanting to shoot NB (Ha, OIII and Hb as you would with your Optolong)?

The Idas LP filters are very good but, as with most things that are very good, they're not that cheap. IDAS LP filter

The RedCat is a Petzval design so almost certainly adding the filter will mean you need to refocus, but I'd be surprised if it was by enough to cause your issues. The Optolong L-enhance is a NB filter so not only will you need to select the right targets to see anything (M81 is probably not one of the best) you will also probably need to take much longer subs than you would be without the filter in (this would account for the banding). I'd try to pick a good emission nebula and try again with a sub of about 2 minutes, then see if you have anything.

Yup agree with Olly. That amount is not an issue and will calibrate out easily. I certainly wouldn't chase trying to reduce or straighten it as you could make matters worse, especially if your stars are good shapes across the FOV. The GIF to me shows things very slightly brighter on the right side, but this could be skyglow or even local lighting source causing this. Running a gradient remover or DBE (in PI) will easily deal with this and again, not unusual at all. APS-C chip is a reasonable size, so what you have here is actually pretty good. Providing you have decent flats taken before moving the camera this will all calibrate out with no issues. I've seen far worse.

The encoders would need to be changed for something with far higher precision, such as renishaw, and then you are getting in to serious money and serious mechanical precision to deal with it. The encoders fitted are high definition, but only sufficiently so to provide an extremely low PE. As quite rightly pointed out by @Zakalwe, guiding is pretty simple if done correctly and is definitely the way to go unless you have big bucks to spend on a mount (tens of thousands) as it takes in to account for what is actually going on, rather than what is theoretically going on.

And without moaning about it!

I don't think price is necessarily a direct or guaranteed recipe for quality. However, as far as filters go, it does seem that the ones which appear to perform more consitently across a specified bandwidth do attract a higher premium. This no doubt is due to the time that goes in to the development and production, but also the materials used and the quality testing (and rejection rates) etc. Ultimatley the right filters for you will depend on your other equipment, environmet (sky quality and light pollution), expectations and realistic capabilities and, of course, budget. All of the above mentioned filters have been shown to produce some superb images on here. The ability of someone with exceptional processing skills and techniques would no doubt eek out far more detail and structure within a given data set from any filter than I can with even 'premium' ones. It is perfectly acceptable, and standard practice, to start with a more cost effective set and then upgrade as your equipment and skill sets provide for you to utilise the potentially better data these higher grade filters can provide you with. However, certainly at the beginning, it is highly unlikely that your choice of filter is going to be your limiting factor, or even amongst them. Best of luck with the venture in to mono, it's a great and very flexible way of imaging.

I like it, Olly, a lot. I think by holding back on the colour in the arms it almost makes your brain work to make it more blue if that is how you prefer to see it, but it doesn't smack you in the face as blue, drawing your eyes away from the whispy dust tentacles and core. Whether Vlaiv's comments are seen as right or wrong when we are simply making pictures I believe is immaterial and for the imager or picture producer to decide, but for me I do think it lends itself to almost forcing you to look at more of the detail rather than just be taken in by the intensity of the colour. Great image and excellent processing as always.

Cheers mate. It's my own fault really as I have an all sky camera sitting in the obsy which I made and haven't installed. This has certainly prompted me to do it now. The Lum data on its own was not too bad, albeit not much of it, so that helped in the end, but the colour was awful 😟 I think I quite like the idea of holding back on the colour and making your brain work to enhance it if you believe it should look different.

Yeah I'm not convinced half hour unguided is realistic, personally. However, with the very low PE I've found guiding very easy indeed. No I've not tried it yet. We were due to go to Spain but things obviously changed somewhat for a couple of reasons. I will be going as soon as I am possibly able and will load the firmware then and try it. Unfortunately it isn't something I can do remotely, as you know 😐

I don't think iOptron ever intended for this to be used unguided, John. I think the encoders are designed simply to reduce the PE to a very low level which makes the guiding much easier with less corrections needed. I love mine and really enjoy using it when I get chance!