Adam J

I would not pay 20 pounds for the amazon one. utter rubbish. Appart from that, I would not recommend a newtonian with a F ratio of less than 5 for planetery / lunar viewing the secondary is too big and the mirrors are cheap and poorly ground in many cases when looking at the very small apertures. https://www.ebay.co.uk/itm/165218291382?hash=item2677c70eb6:g:67UAAOSwl~NhrRLt If going to ebay then that is an astonishing bargain. Adam

Also cheaper here from bristol cameras. Am sure someone like FLO would price match if you asked them. Adam

I think you should buy from a dedicated astronomy shop the guys like picstop at the camera shops dont have any knowledge to support you after purchase if something is not right or you just need help. I would go for a refractor as opposed to the smaller dobs / newtonian reflectors as they just dont perform so well at that end of the market and you are going to be looking at moon and planets anyhow hence long focal lenght refractor is better. So for me that discounts the heritage 100. The most expensive one mercury 705 is by a long way the best package in my option, good mount and scope. Of the others the mercyry 707 is likely the best but the scope but its the mount, no slow motion controls so difficult to point and track an object with the earths rotation, looks flimsy and frankly horrible. its difficult but i promiss you are getting your money worth for that 50 pounds more you would spend. Adam

For just over 100 - something like this maybe https://www.firstlightoptics.com/startravel/skywatcher-mercury-705.html Adam

And thats the problem, a poor scope will ensure that she will not get hooked. A good scope will look at the moon on Christmas day and give a wow factor. A bad one will never come out of the box again.

Any thats the thing, you cant expect a telescope without compromise for under 100 pounds. You really need to spend twice that to get the full package. Adam

if you are very limited on budget watch this. https://www.firstlightoptics.com/celestron-astromaster-series/celestron-astromaster-lt60-az-telescope.html https://www.firstlightoptics.com/celestron-astromaster-series/celestron-astromaster-70az-refractor-telescope-with-smartphone-adapter-and-moon-filter.html https://www.firstlightoptics.com/celestron-astromaster-series/celestron-astromaster-80eq-md-refractor-telescope-with-motor-drive-smartphone-adapter.html depending on budget Adam

Due to them being vertically challenged and the storage requirements I dont actually like Dobs for children. I dont like the small table top ones either as they will struggle not to lean on it and get stable view. If it was my child (it will be in a year or so when he is older) I would go with something like this. As an all rounder. https://www.firstlightoptics.com/sky-watcher-az-pronto/sky-watcher-evostar-90-660-az-pronto.html Or this as a dedicated moon / planet scope. https://www.firstlightoptics.com/sky-watcher-az-pronto/sky-watcher-skymax-102s-az-pronto.html Also of note is that for a child either is good for daylight use with a prism diagonal. Cant do that with a dob. Adam

Only astronomik make such a filter to my knowledge.

Yeah trying to use a Mac for astronomy is only going to limit you. But don't go too modest trust me you don't want to stack 1000 X 30s subs on a duel core processor with 4 gig of ram.

It can but you would need to remove the camera to exchange filters. @PadrePeace is a much better source of information than me on this though as he has that camera.

Really nice images especially m31, yes you need to get those flats working and some sort of light polution gradient removal tool but you have the fundamentals spot on here. Focus is good, framing is good, stars are round. From the number of pixels in the image I am going to guess this is from a ASI294mc pro. I am not sure I would waste too much time on a LP filter for braud band targets like galaxies, to be honest it makes a mess of colour balance and with LED lights wont really help you much. From what you have here the solution is to get flats working and to get a LP gradient removal tool. I use Astro pixel processor for that. When you come to shoot emission nebula targets a duel narrow band filter is the way to go. Your optics look good / well colimated. Lots of fun times ahead for you and a great choice of scope to start out with. Adam

Very nice and welcome to SGL, would be great to see some of your images taken with this setup. Adam

Fantastic presentation of a lesser know region. Wish I could consistently turn out quality images as often as you do. Adam

double post

Speed of capture is all about F-ratio once your camera is fixed. I would say that the GT81 is not suited to the camera you have selected as the chip is too small to cover most wide nebula at the focal length of the GT81. On the other hand you have the GT71 which with its reducer is F4.72 so exactly the same as the GT81 but you will fit a target into the FOV. Lets look at M42 and M31 and M45 the common beginner targets. As above you will not really fit M42 and running man into the GT-81 with the ASI485. The non reduced 61 does better, the GT71 will fit it just but I would say the redcat 51 is there for a referance. M31, only the redcat is going to fit it all in the frame and only the GT71 is wide enough to get M110 into a 2x1 pannel. You can just about fir the main stats into the Gt81 here but not with much room for error in your framing the GT71 will give you more margin or error and the redcat 51 will get some some of the extended stuff that the others are missing compleatly. Other Nebula are much larger than any of these targets, such as NGC7000 (north amrica nebula), the heart nebula etc and only the Redcat 51 will allow you to capture the majority of the target in a single panel. If you have a larger budget sufficient to consider a GT81 ant the required flattener (£1400 total)then I think I would go a different way. I would return the ASI485 if you are still able and I would instead get a ASI533MC Pro cooled camera. The cost of the GT81 - the difference in camera cost will leave you with about 900 pounds for a telescope and flattener. At that point I would go with your original idea of the ZS73 with a 1.0x flattner and you will have a better imaging rig than you would with an uncooled ASI485mc camera and the GT81. If you do keep the ASI485mc because you have to or want to then I really would take the GT71 over the GT81 with that sensor. You may even have enough left over to get a L-extream filter. Remember in imaging the speed of capture is goverend by your choice of camera and F-ratio mainly. Not the aperture, aperture only matters if you dont change focal length and hence you have a faster f-ratio. I would say that none of the scopes you are considering are suitable for smaller galaxies btw, too short a focal length. Adam

There is not really a right answer, but another benefit of the askar is the ample backfocus.

Essentially a WO61 but from ts and discounted. My suggestion is to snap it up mate.

With that small sensor and the small ish pixels you would be better off with the 61 as you will get a wider FOV for emission nebula if that is your thing. If you could push to the GT71 with a reducer then I would say that would be the optimal. For either of the doublets though I would stick with the flattener, doublets arent really optimal when pushed below F6. Something like M42 is much more comfortable in the 61 than the 73 Adam

I have seen it before when only deep red stars produce a halo on some filters.

and yet i just dont see the same quality of images coming out of the 183 as i do the 533. That may be to taist / subjective but I see it as a significant gap not just a small one. What you say is true about exposure length but it would be a significantly longer exposure and for me one of the advantages of CMOS is shorter exposures. I often do 30s exposures with my ASI1600mm pro. I would find the image ideal for the OPs scope with the 533 and a binned 183 to be a little short on pixels for my taist (I like to print my images). Adam

Read noise per unit area is much higher in the 183. Looking at unity gain for both to make my life easier, 2.4um pixels with a 2.2e read noise vs 3.75um pixels with a 1.5e read `noise. If you are doing duel narrow band read noise should be dominant unless you do very long exposures and the 183 does not like that from what i have heard. Pixel area of 533 = 3.75^2 = 14.06um^2 Pixel area of 183 = 2.4^2 = 5.76um^2 Read noise per unit area 533 = 1.5/14.06 = 0.106e/um^2 Read noise per unit area 183 = 2.2/5.76 = 0.382e/um^2 You could go with 2x2 on the 183 = 2.97 / 23.04 = 0.129/um^2 But that's still worse than the 533 even if you further take into account the QE difference. The performance difference will be less significant for RGB imaging of course under less than dark sky as other noise sources will start to dominate and the read noise will be burried. But then you have the 183 AMP glow which to my mind must add noise under that area of the chip and you have the the fact that even if you did go 2x2 in processing you would have worse sampling for no gain and so overall the 533 is just plain better. But the real killer for me is that if you scroll through astrobin the 533 is on average just producing better images. Do you have a different view? Adam

The 533 significantly more sensitive than the 183, also the thing that CCD calculator will not tell you is at a 72mm objective is not able to resolve detail to 1.18 arcseconds per pixel irrespective of the camera you use so you will gain no resolution by going for the smaller pixels of the 183 over the larger more sensitive ones of the 533 which will give you a very respectable 1.8 arcseconds per pixel. The 183 comes into its own in fast large aperture optical systems such as a hyperstar but even then you might still chose the 533. Adam

I cant speak for the samyang apart from having seen many images from it and noting that for me it just seems to just miss that ~200mm sweet spot for resolution and FOV. If you really want speed go for the samyang, but if you want a detailed image the ASKAR is better. You will want to budget for an L3 filter with it though due to the CA, that aside I am really very happy with mine. What I would say to ASKAR though is that as most people are laying down another £100 for a filter to sort out the CA, a more premium ED glass might work better and on only a 40mm lens be cheaper than the combined cost with a filter. Hence I would encourage a change of design moving to FPL53, FCD100 or FLP55 even if it adds another £100 to the cost of the scope. Adam