Mr Thingy

Does anyone know if the fitting is the same between Canon EF, EF-S and EF-M lenses?

I'm trying to figure out if the adaptors for fitting Canon lenses to CMOS cameras will work for the EF-M lenses. e.g this:

https://www.firstlightoptics.com/adapters/skywatcher-dslr-m48-ring-adapter.html

The EF-M lenses are cheaper and are for the smaller format, which seems like it would suit my ASI 183 sensor.

TIA

5 hours ago, Alien 13 said:

I can offer some answers.

Nikon or Canon, quality wise nothing in it although Canon might be a bit cheaper. The Canon lenses do have a big advantage with their longer backfocus making it easier to fit filters into the light path.

The later Canon/Nikon or Sigma lenses operate with "fly by wire" systems so are totally unsuitable as the aperture and focus require the lens to be powered up to operate.

The Samyang range of lenses are well received and are totally manual but not cheap or you could look at the old M42 film camera lenses from takumar/minolta etc. 

Alan

Many thanks. That's helpful.

Hello SGL-ers!

Looking for some advice from you kind, knowledgeable people.

My HEQ5 is taking an eternity to arrive (1/4 of a year so far) and I'm not convinced it will even arrive in Dec so I'm exploring options that will allow me to take some snaps in the meantime.

I was considering buying a camera lens for some static-mount, wide angle imaging, to attach to my ZWO ASI 183 GT. I can then use guided/unguided when the HEQ5 arrives.

I was thinking about a lens with a FL of about 35  to 50 mm. 

My first question is whether it is suitable to get a lens for the smaller sensor size (e.g Canon APS-C)? My CMOS camera has a diagonal of about only 16 mm, so it seemed that with a standard lens for full frame (35 mm), my sensor would only capture half of the image.

My second question is how best to attach to my mount. Can you get a bracket to attach to the lens (maybe a mounting ring from a scope would work)?

Last question: is there any notable difference between Canon or Nikon lenses? Is one better suited to AP than the other.

I was looking at this (and the 35 mm equivalent):

https://www.intro2020.co.uk/Catalogue/ProductDetail/samyang-50mm-f1-2-csc-canon-m?productID=caaea451-50fb-4d26-8ed6-f4718d906c5d&catalogueLevelItemID=376dc0a0-f0a7-422d-a66b-27282b4cce5b

All other comments and recommendations welcome; come earn yourself some of the reputation points I know you love!

TIA

-Thingy-

I bought an adaptor and a bunch of extenders and now everything works perfectly (I also learned a wee bit more theory on telescopes and focus) 😀

Thanks for all the great advice!

Thoroughly exciting item received today. So exciting that I will share with you all. 

The sad part is that it's going to sit idle until my HEQ5 finally turns up (ordered mid-Aug) 😪.

Dear China, please make and ship my HEQ5 ASAP. Tyvm.

-Thingy-

FLO will love me this year. 

This hobby is expensive!

3 minutes ago, alacant said:

Yes. that will do fine. Remember that you also need some distance inside the 72ed so that you can clamp it.

After a few year's doing this for any telescope which comes along, you end up with this number of extension tubes. The fewer you have, the more likely you are to fail!

 

 

Awesome. Thanks a lot.

4 minutes ago, alacant said:

HTH

That helps immensely. Thanks for your explanation. 

I knew I'd have some silly questions sooner or later!

If I'm not using an FF, do you know how much extension I need to achieve focus? Is that still 130mm?

53 minutes ago, alacant said:

Hi

Don't confuse back focus with position of focus relative to the telescope body or camera back focus. The shoulder of the ff needs to be 130mm from the camera sensor. That's it. Set that, then decide on a sensible focus position.

Thanks. I think I'm missing a key bit of theory here as I'm still confused. 

I thought that it would simple be a case of finding the distance behind the scope where the image is in focus. What is the 130mm position then? Is it the point where the image is the correct size for the sensor?

Then how do you set a focus position?

Maybe there is a website that explains this?

Cheers

9 hours ago, alacant said:

We use this one with the 72ed. It has the advantage of retaining native focal length and gives you a whopping 130mm back focus. No extra colour or vignetting is introduced and the stars are good to the corners. Well, as good as cheap SW refractors allow!

Yes, it's in stock.

Cheers

Thanks @alacant 

Do I understand that with the TS flattener I would still need extenders to reach the 130mm back focus?

What would you use for that?

Everywhere is sold of field flatteners at the moment.

Looks like my mount won't be the last thing I'm waiting for before I can start imaging 😓.

Anyway, thanks for all be the great help. Have yourself some rep points for your troubles 😄

3 minutes ago, Skipper Billy said:

It should have - mine does !!

You will probably need one of these to make adding extensions cheaper and easier - the M54 thread on the focuser drawtube is an relatively uncommon size

https://www.firstlightoptics.com/adapters/astro-essentials-m42-t-adapter-for-sky-watcher-newtonians-and-72ed-refractor-m54.html

Do you have to remove the bracket for the 2” nosepieces to find the thread? 

I tried earlier but it wouldn't budge and I didn't want to force it.

Cheers

20 minutes ago, Skipper Billy said:

The end of the focuser is threaded - this is an all screw together system - you will need about 4" of extension.

 

 

Unless I'm missing something the 72ED doesn't seem to have a screw thread at the end of the focuser. I assumed there would be.

14 minutes ago, dodgerroger said:

FLO do a camera rotator for the 72 then a field flattener can be screwed to it. I use a generic 2” flattener and some small spacers to achieve back focus and round stars to the edge

Which generic flattener/reducer do you use? I notice that FLO have a 40-60 working day wait on the dedicated reducer for the 72ED. My HEQ5 had the same estimate when I ordered in mid-August and that's not here yet, so it's not looking good for the reducer 😓.

50 minutes ago, alacant said:

Hi

Unless you use a focal reducer, you're going to need about 130mm of extension between the two to reach adjustable focus at infinity. 

HTH

 

Ah! Ok, good to know. Thank you.

In that case I will be needing a focal reducer. No sense in buying umpteen extenders for temporary use.

Any idea how the focal reducer attaches to the scope? There seems to be no thread on the scope.

I thought I was missing something obvious but it looks like just a bit of tinkering is needed. Thanks to all.

Pretty sure this is a stupid question but I have to be asked as I can't figure this out myself 🤔

I have a SW Evostar 72ED and a Guidestar 50ED that will be the guidescope. I don't want to attach the 50ED using the finderscope shoe as I foresee a scenario involving gravity, the floor and some expensive gear, so I want to mount directly onto the top of 72ED.

However, I can't see how this should be done, so I'm looking for tips. The ED has a dovetail - do I need to replace with a different plate? 

Thanks in advance kind people of greater brain power than my own 😉

15 minutes ago, AstroExploring said:

I own the 72ED but use it with a DSLR currently. You need 55mm backspace between the back of the scope and the camera. The easiest way to achieve this is to buy the field flattener (noting you don't have one yet). You could try a 2 inch t-adapter? That would give you enough spacing, you'll just need the right adapter to then attached your 183. I don't know if such an adapter exists - sorry, I've only ever used a DSLR. Somebody more knowledgeable might know 🙂

Thanks. It's helpful to know that I need 55mm of backspace. The extenders from the camera are only 28mm combined and I lost half of that slotting into the 2" hole.

I need to figure out a means to screw the m48 extenders directly to the scope without inserting in the 2" slot.

I suspect more money is needed to find s solution. This sport is a money pit (as if I didn't realise that already!)

I have various extenders and adaptors but I don't seem to have enough to achieve focus with the 72ED and my ZWO ASI183 GT.

Can any owners of a SW Evostar 72ED advise what extenders and adaptors you use to achieve focus? Please note that I don't yet have a field flattener fitted - I will get one fairly soon but for now I need a solution without one.

I was also hoping that there would be a screw thread for secure fitting between scope and camera but the 72ED only seems to have a 2" fitting for diagonals, etc.

Thanks for any advice you can provide.

7 hours ago, andrew s said:

Ask that the wood is put to use. As a hard wood it had uses in interiors but lacks durability externally. This way the CO2 release will be long delayed. 

Regards Andrew 

Excellent idea. 😀

33 minutes ago, JamesF said:

I appreciate your point of view, though I'm no particular fan of sycamore I have to admit.  We have a lot of it around here and it feeds a lot of aphids which in turn attract other insects and birds such as swallows (which I do love to see).  However, it's also hideously invasive to the point of almost being a weed.

In your situation I think I'd be inclined to say that you can accept that it may not be the ideal tree to have in their garden but it's a shame to completely remove something that provides a home and food to so many animals and why don't they consider planting a different tree (or two) to replace it (not necessarily in the same location).  It could be an ornamental tree, but perhaps a fruit tree on a rootstock that will keep it to a manageable size and which will also feed many insects might provide more enjoyment.  If they won't run with the idea then they won't, but if they do then it's at least some small mitigation for the removal of the sycamore.

James

I've no doubt they will replace it; and surely with something more appealing. I too am not a big fan of sycamore, but the shame is that it's old - at least 50 years I would guess - and any replacement will take a long time to reach the same canopy size and leaf density, not to mention the same CO2 intake. 

Though I won't miss the tonne of leaves that somehow seems to land in my garden rather than theirs each autumn.

I have a slightly different quandry, but still related to the topic of nature. 

My neighbour has asked if we have objections to removal of a massive sycamore tree from their garden. I have mixed feelings as this thing blocks my NE view but it's also a great habitat for bird and insect life. Such a massive tree can't easily be replaced, of course.

Since objects tend to rotate into view from the NE anyway, the tree isn't much of an embuggerment for me when observing. 

It's ultimately their choice, though I could in theory contest during the planning application, but I think I will just tell them that it would be a big shame to remove it and let them make the choice. Hoping they make a sensible decision. 

12 hours ago, Chefgage said:

I seem to be buying an item of astro photography gear every week now. I get a bit fitted then think mmm I need that bit on the mount now!

Ha yes! I know the feeling. I just ordered the EAF, so now my rig will be fully automated 😀.

I can now cross one more thing off my shopping list. My wife will be so pleased.

15 minutes ago, Chefgage said:

I needed an extension for my Canon 200d DSLR. Without it I could not get focus. The general recommendation for this scope is a flattener of course. I used an OVL field flattener which gives me the correct distance to gain focus. So it it does 2 things at once, gives me focus and flattens the image.

Ah yes, the flattener. That's on my ever-growing shopping list of astro gear. I also plan to get an EAF to attach onto this.

19 minutes ago, Chefgage said:

Enjoy the 72ed, I certainly like mine.

Thank you. I plan to play with it at the weekend and figure out if I need any extra extenders for my camera.