50 replies to this topic

[StormRyder]

Hello, I do not want to take over this thread but I have a very closely related question/issue.  If it is better for me to post in a separate thread, let me know. I recently obtained a SW ST120 as my first scope, I have no other equipment. I'm learning to star hop. The 45deg diagonal is tricky to use when looking up, so I've acquired a Baader 2" Clicklock diagonal. I intend to get 2" EPs down the road.  I got the chance to use the new Baader diagonal for the first time tonight but I cannot achieve focus. When I pointed to one of the 3 starts on Orion's belt, I see a fairly large bright circle, taking the majority of the view from the 25mm eye piece. I cannot turn the focus knob enough to change this. The 25mm eye piece that I use is the one provided with the scope and since it is a 1.25", I used the adapter that was installed before the 45 diagonal into the scope, it is now in the eye piece side of the Baader diagonal.  Is the focus issue because of this adapter?

Edited by StormRyder, 30 March 2021 - 12:28 AM.

[ilan_shapira]

Hello, I do not want to take over this thread but I have a very closely related question/issue.  If it is better for me to post in a separate thread, let me know. I recently obtained a SW ST120 as my first scope, I have no other equipment. I'm learning to star hop. The 45deg diagonal is tricky to use when looking up, so I've acquired a Baader 2" Clicklock diagonal. I intend to get 2" EPs down the road.  I got the chance to use the new Baader diagonal for the first time tonight but I cannot achieve focus. When I pointed to one of the 3 starts on Orion's belt, I see a fairly large bright circle, taking the majority of the view from the 25mm eye piece. I cannot turn the focus knob enough to change this. The 25mm eye piece that I use is the one provided with the scope and since it is a 1.25", I used the adapter that was installed before the 45 diagonal into the scope, it is now in the eye piece side of the Baader diagonal.  Is the focus issue because of this adapter?

You need to check if you are missing in or out focus. I believe your need out focus and for that you can get an extender which is cheap.

Focus all the way in and start your way out. check in which point the stars are more focused - smaller.

If they are best when focuser is in, remove the adapter and connect the diagonal directly if possible.

If its the other way around, you can add extender (or spacer) to place the diagonal away from the lens.

[Jon Isaacs]

Thanks for all the inputs, everyone.  The picture from Ilan is very helpful.  From what I can see, it looks like the main effect is around the edge, but on the surface, I can't say that I see any real obstruction of detail.  I was thinking the whole surface would be double or triple imaged, with every crater having a shadow crater beside it.  Does t get a lot worse at higher powers?

 

 

You primarily see the purple haze around the edge, that's the red and blue ends of the spectrum that are out of focus.

 

What chromatic aberration does to a planetary image is smear the finer details because the colors are out of focus.  It's definitely more visible at normal planetary magnifications.

 

The moon is a high contrast object so a fast achromat can do a respectable job.

 

I thought Bobhen's post was a good assessment of a scope like this.  If you primarily use it at low to medium powers for DSOs and occasionally for casual glances at the planet's with minimal expectations, it can be an effective scope. For DSOs, the CA has a minimal effect.

 

If you're looking for a scope that is an all-arounder, capable of good planetary views with a minimum of chromatic aberration but still capable of wide field views, then something like the Astro-tech 102ED might be a better choice. 

 

Under dark skies, a fast achromat is a good companion for your 8 inch or 15 inches.  The refractor excels at the lower power views not possible with the larger scope and the larger scope handles the higher power views including the planet's where the false color might get in the way.  

 

Jon

[StormRyder]

You need to check if you are missing in or out focus. I believe your need out focus and for that you can get an extender which is cheap.

Focus all the way in and start your way out. check in which point the stars are more focused - smaller.

If they are best when focuser is in, remove the adapter and connect the diagonal directly if possible.

If its the other way around, you can add extender (or spacer) to place the diagonal away from the lens.

I went out and tried again.  No luck. Below is my setup.

When it is extended as shown in this image, I can focus to something rather close.  For example in the living room, I can focus on something in the kitchen.

When looking at the stars, they get smaller as it diagonal gets closer to the telescope. But I cant get anywhere close to what it needs to be. Stars remain very large, like size of a pea, not like the point of a needle as it should be.

 

The diagonal is all the way in, except for this black ring holding it, I don't know if something else exists that I should use instead ?

I don't know what effect the adapter would have that is between the diagonal and the eye piece, does it play a role in this issue?

 

I see here, someone else having issues with a 2" diagonal: http://www.waloszek....ro_sw_120_e.php

Edited by StormRyder, 02 April 2021 - 11:04 PM.

[bobhen]

It "might be" that the adapter is too tall - taking up focus travel.  Try using just a 2" eyepiece. If that works, you will need to purchase a lower profile adapter. You can also purchase a GSO 2" Focuser to replace the standard focuser. The GSO focusers are much shorter than the standard focuser and are better quality as well. They only take 5 minutes to instal. 

 

Bob 

[StormRyder]

It "might be" that the adapter is too tall - taking up focus travel.  Try using just a 2" eyepiece. If that works, you will need to purchase a lower profile adapter. You can also purchase a GSO 2" Focuser to replace the standard focuser. The GSO focusers are much shorter than the standard focuser and are better quality as well. They only take 5 minutes to instal. 

 

Bob 

Been researching this today, yea in all likely hood, a GSO focuser will resolve this.  I've found many posts about this topic. So that is a heads up for anyone who wants to go to 2" EPs with the ST120, you are likely going to need a shorter focuser.  I personally was not expecting that, it is written in many places this accepts a 2" diagonal and a few people recommend going that route, but never saw any mention of replacing the focuser, at least not for this specific reason. And FYI, I removed the original one, measured the tube to be a bit less than 4", so that means I need the 96.6mm version. I have a support ticket at skywatcher; hoping they will confirm the need for a shorter focuser and not contradict everything I have been reading today. It also seem that I will not need to get an extender as once I move to the 2" EPs, it will not be needed and Im not planning to use any 1.25" EPs after that, which those would need an extender.  I read the stock focuser has a built in 30mm extension.

 

And when you get a GSO focuser, then you have to get a new shoe for the red dot finder.

 

I do not have any 2" EP yet to see if that would alleviate the issue. I have my eyes on a Baader zoom, so I will get one now at same time as the new focuser.

 

I was hoping to do this 2" upgrade step by step but it seems it is an all or nothing kind of thing.

[ilan_shapira]

Thats very interesting and unsettling. I will ask one of my astro group members who uses the 120 for few years. I am sure he is using 2" diagonal and did not replaced the focuser.

[LDW47]

Been researching this today, yea in all likely hood, a GSO focuser will resolve this.  I've found many posts about this topic. So that is a heads up for anyone who wants to go to 2" EPs with the ST120, you are likely going to need a shorter focuser.  I personally was not expecting that, it is written in many places this accepts a 2" diagonal and a few people recommend going that route, but never saw any mention of replacing the focuser, at least not for this specific reason. And FYI, I removed the original one, measured the tube to be a bit less than 4", so that means I need the 96.6mm version. I have a support ticket at skywatcher; hoping they will confirm the need for a shorter focuser and not contradict everything I have been reading today. It also seem that I will not need to get an extender as once I move to the 2" EPs, it will not be needed and Im not planning to use any 1.25" EPs after that, which those would need an extender.  I read the stock focuser has a built in 30mm extension.

 

And when you get a GSO focuser, then you have to get a new shoe for the red dot finder.

 

I do not have any 2" EP yet to see if that would alleviate the issue. I have my eyes on a Baader zoom, so I will get one now at same time as the new focuser.

 

I was hoping to do this 2" upgrade step by step but it seems it is an all or nothing kind of thing.

When you use 2” low power eps you don’t need a finder, your scope becomes the finder.  Many ST owners go that route !

[StormRyder]

Thats very interesting and unsettling. I will ask one of my astro group members who uses the 120 for few years. I am sure he is using 2" diagonal and did not replaced the focuser.

Sky-Watcher replied on my support ticket.  They said they replicated by setup and confirmed the focus issue.  But they said it is due to the adapter that I use (the on that came with the telescope).  They say it is designed to go before the diagonal, not after. They used a thinner adapter and it worked for them using different kinds of eye pieces.

 

I'm going to order a 2" EP and see if that work as they say it should.

[MikeTahtib]

Well I did it.  Skywatcher 120AZ3 on the way, with a 2" GSO diagonal.  I was concerned about StormRyder's problem, as I did not want to have to add a new focuser  just to get it to work.  After I saw his post, I decided to order.  I am a bit concerned about John Isaac's comments about the mount not balancing well, but I'll see what happens.  I can always make some sort of Rube Goldberg balancer to hang off the front and below the pivot point, maybe clamped between the scope rings and mount.  Although I'd rather not have to do that, since this is supposed to be a fun-and-easy scope. 

I considered waiting for the Orion to become available again.  It may be a better setup, but their treatment of owners of second-hand Orion gear really rubs me the wrong way.  I called Skywatcher and asked what their policy was towards people needing spare parts for their gear.  I was told they sell to whoever needs a part. That's the kind of company I want to support.

Thank you to everyone for all your valuable advice.

Edited by MikeTahtib, 05 April 2021 - 10:10 PM.

[kksmith]

Be prepared to replace the mount in short order. When I bought my SkyWatcher 102, it came with the AZ3 tripod mount minus legs. I was keen on trying the slo-motion feature, so I stuck on a set of legs I had. That only lasted one observing session. No amount of tightening would keep the Scope from pivoting backwards to zenith or forward butt end up. I replaced washers, nuts - but I still need a wrench constantly. Having a 2 speed Crawford on my scope probably didn’t help any, but still the mount should have handled it. The AZ3 is nothing more than a display mount in my mind. The scope quickly went back on my Twilight mount. Now it’s getting ready to ride on Stellarvue’s MC2 mount.

Edited by kksmith, 06 April 2021 - 04:06 AM.

[Skookumrob]

Just wanted to chime in about the mount. My SW 120 works well with the provided AZ3 mount and stand. No trouble even at 150x using tracking with fine controls, not too much shaking or anything. I also do my observation on a wooden deck. In terms of balance I have no issues at all even using heavy 1.25 inch eyepieces such as my Antares series 13mm eyepiece with a Barlow or my celestron 8-24x zoom also barlowed. I am currently awaiting an Antares 2 inch diagonal and 31.5mm 2”eyepiece. I will update any balance issues or focussing problems when those arrive. I am only posting due to all the problems I had trying to find information about the scope combination before I bought it. There are lots of answers by people who do not have the scope suggesting what you can and cannot view with it. Hopefully we can get more answers from people who actually do you have the scope about what you can see and not see and what the view looks like.

[Skookumrob]

So the Antares 2” diagonal and Antares series 2 speers-waler 31.5mm 2” eyepiece have arrived and the balance is still good. The nylon locknut DID require a tiny adjustment (tightening) but this has not affected either the manual movement or the fine adjust movement at all. Both are still smooth. Gotta say I am super stoked to try this new eyepiece with its 90 degree FOV out tonight. During my looking through it today at terrestrial targets it is super crisp edge to edge. No negatives whatsoever to report! These Antares eyepieces are fantastic in this scope. I also have the 13mm Series 3-80degree FOV which is great so far too (only had it a couple days too as they were ordered at the same time). Very excited to take them out somewhere with more available views and darker sky’s than my back deck! I am very interested to see how they do with the moon and Jupiter!

[StormRyder]

Sky-Watcher replied on my support ticket.  They said they replicated by setup and confirmed the focus issue.  But they said it is due to the adapter that I use (the on that came with the telescope).  They say it is designed to go before the diagonal, not after. They used a thinner adapter and it worked for them using different kinds of eye pieces.

 

I'm going to order a 2" EP and see if that work as they say it should.

I now have a Baader Zoom and can confirm the focusing issue went away.  So it was the adapter after all, no need to change the focuser.

 

However, I have a new issue.  With the Baader 2" diagonal and zoom, when pointing near zenith, the mount does not hold position. Perhaps is just a tightening issue, haven't had chance to investigate this. Other than that, I also don't really have any issue with this mount.  It feels flimsy but it works fine. I don't even use the tray so I can collapse it really quickly to get in-out of the house.

 

Perhaps of interest to others, I have ordered this item: http://www.scopestuff.com/ss_fas2.htm

I'm not a fan of how the diagonal just holds in the focuser with just two thumbscrews. It may be fine, but I'm not taking the risk of the equipment falling to the ground  . Should show up tomorrow. As a added benefit, it will add a bit of in-focus as it is shorter than the one provided. with the scope.

[bobhen]

 

 

However, I have a new issue.  With the Baader 2" diagonal and zoom, when pointing near zenith, the mount does not hold position. Perhaps is just a tightening issue, haven't had chance to investigate this. Other than that, I also don't really have any issue with this mount.  It feels flimsy but it works fine. I don't even use the tray so I can collapse it really quickly to get in-out of the house.

 

 

If the AZ3 mount is slipping when pointed high or near zenith, it is most likely a balance/altitude axis/tightening issue.

 

Balance the scope at around 45-degrees. When pointed lower or much higher, slippage can occur because the balance point is not now directly over the mount.

 

One solution is to replace the lock nut on the altitude axis with a large wing nut. With the wing nut, you can adjust the tension on the altitude axis in the field as needed without any tools.

 

Bob

[MikeTahtib]

Well, I got the telescope early this week, and of course it's been mostly cloudy since.  It's even snowing right now. 

 

First Impressions  - The telescope arrived well packed and damage free.  It assembled quickly and easily.  It looks impressive, not toy-like at all. The tripod seems quite sturdy. I also got a  GSO 2" diagonal, so I installed it right away, without trying the included 45* 1.25" prism. 

 

My main concern was that it wouldn't balance when pointed toward the zenith.  I loaded my 30mm 82* Explore Scieintific eyepiece into the GSO diagonal and tipped it up, and it held.   This is mainly due to the altitude bearing being set from the factory very tight.  While this seems to prevent  the scope from flopping backwards when pointed up, it also makes for stiff pointing of the scope.  It is definitely not like swinging my Obsession around.  I have the scope installed forward in the rings to balance heavy eyepieces, but the scope still balances with no eyepiece installed.

 

The supplied red dot finder was easy to adjust to align with the telescope, and so far has stayed in adjustment.  It has a dimming function, but I suspect it will still be brighter than I would like for a dark site.  I may consider mounting a Telrad, or maybe opening the red-dot and seeing where I can add a resistor in to dim it down.

 

I did get it outside for a couple minutes on Tuesday before all the holes in the clouds closed up, and got a look at open cluster M38 (I think) in Auriga.  It was visible as a shiny spot on the sky. I did not notice any chromatic aberration on stars that were visible.  Everything looked good, really.

 

The next night I did all the things i wasn't supposed to do with a telescope like this for a torture test.  I spent some time on a very thin crescent moon.  I was very pleasantly surprised at the results of this.  I tried almost all my eyepieces, from 30mm all the way to 4.7mm w/ a 2X barlow.  They all came to focus, and all showed good detail on the lunar surface.  The crescent was so small, there wasnt' too much to see, but what was there was reasonably nice, even up to 256x.   

 

I then turned to Sirius, which appeared as a rainbow of colors on a blue disc.  That was disappointing, but not unexpected, so I took the barlow off, and put the 4.7mm back in; maybe a bit better, but still not very stellar.  At that point, the clouds rolled in again. 

 

So very low power, nice views of stars as expected.  Very high power, not so nice views of stars, again as expected.  But good high power views of the moon are an unexpected surprise.

 

In use, the scope was a bit tight and sticky to point, making it difficult sometimes to get right on the target, but the slow-motion controls worked well to dial it in and track.  While I had expected to point the scope directly and use the hand controls only for fine centering and tracking, changing my approach to getting it roughly in the right area, then using the hand controls to align while looking through the red dot works well.  Sweeping in Azimuth is easy; sweeping in altitude maybe not so much.  The focuser worked smoothly; really, it exceeded my expectations. 

 

The eyepiece tray attaches with 3 loose thumbscrews, from the bottom, which I'm a little disappointed in.  It takes a bit of time, and I can see them getting lost easily.  I would have preferred some sort of captive fastener that cant' get lost.

 

So far, I'm happy with the telescope.  I can easily lift the whole thing up fully assembled and walk out my door with it.  It has already allowed me to see things I would not have seen with my other telescopes; not because it has superior optics, but because I would not have taken either of my other telescopes out to look at the crescent moon or a star cluster for just a few minutes. 

[LDW47]

I now have a Baader Zoom and can confirm the focusing issue went away.  So it was the adapter after all, no need to change the focuser.

 

However, I have a new issue.  With the Baader 2" diagonal and zoom, when pointing near zenith, the mount does not hold position. Perhaps is just a tightening issue, haven't had chance to investigate this. Other than that, I also don't really have any issue with this mount.  It feels flimsy but it works fine. I don't even use the tray so I can collapse it really quickly to get in-out of the house.

 

Perhaps of interest to others, I have ordered this item: http://www.scopestuff.com/ss_fas2.htm

I'm not a fan of how the diagonal just holds in the focuser with just two thumbscrews. It may be fine, but I'm not taking the risk of the equipment falling to the ground  . Should show up tomorrow. As a added benefit, it will add a bit of in-focus as it is shorter than the one provided. with the scope.

With an AZ3 its the nature of the beast with altitude slippage, to stop it you have to really tighten down that big centre nut / bolt and then you have to contend constantly with the lack of full travel in the alt controls ie reset them ! Have a look at the Porta II and your troubles are over !

[LDW47]

If the AZ3 mount is slipping when pointed high or near zenith, it is most likely a balance/altitude axis/tightening issue.

 

Balance the scope at around 45-degrees. When pointed lower or much higher, slippage can occur because the balance point is not now directly over the mount.

 

One solution is to replace the lock nut on the altitude axis with a large wing nut. With the wing nut, you can adjust the tension on the altitude axis in the field as needed without any tools.

 

Bob

With the AZ3’s alt holding problem, to be able to tighten it down with a wing nut without using tools you must be a very strong guy, I am and I had a problem, when I had my 3 ! Its a plain poor design and the alt controls, the travel distance is no better ! You get what you get !

[LDW47]

Well, I got the telescope early this week, and of course it's been mostly cloudy since.  It's even snowing right now. 

 

First Impressions  - The telescope arrived well packed and damage free.  It assembled quickly and easily.  It looks impressive, not toy-like at all. The tripod seems quite sturdy. I also got a  GSO 2" diagonal, so I installed it right away, without trying the included 45* 1.25" prism. 

 

My main concern was that it wouldn't balance when pointed toward the zenith.  I loaded my 30mm 82* Explore Scieintific eyepiece into the GSO diagonal and tipped it up, and it held.   This is mainly due to the altitude bearing being set from the factory very tight.  While this seems to prevent  the scope from flopping backwards when pointed up, it also makes for stiff pointing of the scope.  It is definitely not like swinging my Obsession around.  I have the scope installed forward in the rings to balance heavy eyepieces, but the scope still balances with no eyepiece installed.

 

The supplied red dot finder was easy to adjust to align with the telescope, and so far has stayed in adjustment.  It has a dimming function, but I suspect it will still be brighter than I would like for a dark site.  I may consider mounting a Telrad, or maybe opening the red-dot and seeing where I can add a resistor in to dim it down.

 

I did get it outside for a couple minutes on Tuesday before all the holes in the clouds closed up, and got a look at open cluster M38 (I think) in Auriga.  It was visible as a shiny spot on the sky. I did not notice any chromatic aberration on stars that were visible.  Everything looked good, really.

 

The next night I did all the things i wasn't supposed to do with a telescope like this for a torture test.  I spent some time on a very thin crescent moon.  I was very pleasantly surprised at the results of this.  I tried almost all my eyepieces, from 30mm all the way to 4.7mm w/ a 2X barlow.  They all came to focus, and all showed good detail on the lunar surface.  The crescent was so small, there wasnt' too much to see, but what was there was reasonably nice, even up to 256x.   

 

I then turned to Sirius, which appeared as a rainbow of colors on a blue disc.  That was disappointing, but not unexpected, so I took the barlow off, and put the 4.7mm back in; maybe a bit better, but still not very stellar.  At that point, the clouds rolled in again. 

 

So very low power, nice views of stars as expected.  Very high power, not so nice views of stars, again as expected.  But good high power views of the moon are an unexpected surprise.

 

In use, the scope was a bit tight and sticky to point, making it difficult sometimes to get right on the target, but the slow-motion controls worked well to dial it in and track.  While I had expected to point the scope directly and use the hand controls only for fine centering and tracking, changing my approach to getting it roughly in the right area, then using the hand controls to align while looking through the red dot works well.  Sweeping in Azimuth is easy; sweeping in altitude maybe not so much.  The focuser worked smoothly; really, it exceeded my expectations. 

 

The eyepiece tray attaches with 3 loose thumbscrews, from the bottom, which I'm a little disappointed in.  It takes a bit of time, and I can see them getting lost easily.  I would have preferred some sort of captive fastener that cant' get lost.

 

So far, I'm happy with the telescope.  I can easily lift the whole thing up fully assembled and walk out my door with it.  It has already allowed me to see things I would not have seen with my other telescopes; not because it has superior optics, but because I would not have taken either of my other telescopes out to look at the crescent moon or a star cluster for just a few minutes. 

You will love the scope, the mount ?

[sportsmed]

Glad you got it in and was able to get first light, if you know your expectations and let the scope shine where it can you are going to really enjoy it and it will make a good companion to your big dob. I tend to take my smaller scopes out 95% of the time compared to my dob just because of how easy they are to transport and setup. And they are great for those times you dont want to view very long and dont want to hassle with a big scope. Congrats on the new scope..clear skies!

[bobhen]

Reread my post number 4 and you will see that your experience matches what I posted.

 

Read my post number 40 for a quick fix that will help with the AZ3 mount’s altitude axis tightening. The AZ3 is fine for one object observing like lunar observing but is less convenient for deep sky sweeping. It can work, but there are better solutions.

 

Below is an image of the wing nut I used on an AZ3. It's hard to see, but the the "wings" are large and can easily be tightened by hand.

 

I’m sure you will enjoy the 102 F5.

 

Bob

Attached Thumbnails

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[LDW47]

Reread my post number 4 and you will see that your experience matches what I posted.

 

Read my post number 40 for a quick fix that will help with the AZ3 mount’s altitude axis tightening. The AZ3 is fine for one object observing like lunar observing but is less convenient for deep sky sweeping. It can work, but there are better solutions.

 

Below is an image of the wing nut I used on an AZ3. It's hard to see, but the the "wings" are large and can easily be tightened by hand.

 

I’m sure you will enjoy the 102 F5.

 

Bob

So what do you use to hold the head of the bolt with, two fingers, while you strongly tighten the wing nut down ? I would like to see that, from my extensive experience with the amount of tightening required to control the alt, to keep it from falling back ! You are surely one lucky guy !

[LDW47]

The OP may get it tightened down like we all do / did but it won’t be long until it starts slipping backwards, hard tightening with two wrenches is the only way ! Its a never ending battle !

Edited by LDW47, Yesterday, 06:43 PM.

[bobhen]

So what do you use to hold the head of the bolt with, two fingers, while you strongly tighten the wing nut down ? I would like to see that, from my extensive experience with the amount of tightening required to control the alt, to keep it from falling back ! You are surely one lucky guy !

I used the AZ3 for years mainly as my mount for solar observing. The wing nut can be tightened or loosened with one hand. It doesn’t have to be overly tightened just tight enough to do the job. It's not a perfect solution because the mount is not designed correctly but it makes adjustments easier to do in the field.  Luck has nothing to do with it.

 

Bob

[LDW47]

I used the AZ3 for years mainly as my mount for solar observing. The wing nut can be tightened or loosened with one hand. It doesn’t have to be overly tightened just tight enough to do the job. It's not a perfect solution because the mount is not designed correctly but it makes adjustments easier to do in the field.  Luck has nothing to do with it.

 

Bob

Thats not my experience with the amount of tightening required with my 3 AZ’s ! But I have said enough, if the OP is happy with what he is hearing then so am I. I say again Good Luck !