planetary observation

[JOHN BENNETT]

I recently obtained a Skywatcher Skymax 102 and Synscan goto AZ/Alt mount. I chose this scope because I want to observe planets and moon primarily and dabble in astrophotography.

So far I have had some early success observing the moon and setting up prime focus shots using my Nikon DSLR. This is useful in preparation for planetary work. However I am waiting for Jupiter and Saturn in particular to rise at a more convenient time later in the year here in the Southern hemisphere (not too good at 4 AM). Meanwhile I've been looking at websites that illustrate the field of view with my scope and various focal length eyepieces. The kit included a 10mm and 25mm Skywatcher 'super' EP and a Skywatcher 2x Barlow. I assume these to be basic and have added a 32mm and 15mm EP of better quality.

When I enter this data into the FOV chart I was disappointed to see how small the images are for Jupiter and Saturn at 173x. This is using the 15mm and 2x Barlow. Using the 10mm increases mag to 260x which I understand is beyond the scope's capacity. Is this the best I can expect from the 102 ? It seems pointless going to shorter focal length EP's. What mag is necessary to get a decent image of these planets ?

Maybe I've made a mistake - should have gone for the 127 ? Or can I expect to get an acceptable result by taking video and stacking the individual frames ? A lot of questions here !!  

[Cosmic Geoff]

I suggest you look in the 'Planetary Imaging' sub-section of this forum and see what the imagers getting great results are actually using.

Briefly, the eyepiece magnification is not really relevant to imaging these planets. Also, getting the best eyepiece view takes some skill and experience. And yes, these planets do look quite small even at the highest usable magnification. A 102 Mak is on the small side for planetary imaging, though you will get a result. You should use a dedicated planetary imaging camera rather than a DSLR.  Once you have mastered the techniques, you may well find that the results surpass what you can see visually.

[Ags]

I have a Skymax 102 and it is a great scope for planets and Moon. I typically use a 10 mm eyepiece with no barlow - this is more than enough to show lots of detail on Jupiter while still keeping the image bright enough for contrast and color. In fact I often use a 16 mm eyepiece as the brighter image is easier for my aging eyes - and this still shows nice detail and color.

I can go a little bit higher on the Moon, Saturn and Mars - for those I can use a 7 mm eyepiece (again no barlow).

I have done some astrophotography with it, and I have attached some of my shots.

Edited May 14, 2020 by Ags

[Ags]

Not my picture, but this is an impressive result for the Skymax 102:

https://www.astrobin.com/291112/?nc=all

[RT65CB-SWL]

Hi @JOHN BENNETT and welcome to SGL.

I agree with @Ags has said above; although my small Mak is a 're-modded' ETX105; (image below)...

   

The smallest eyepiece I use is a TeleVue 6mm Radian or Circle-T 6mm Ortho. At a pinch, I can get away with the TeleVue 3-6mm Nagler zoom at 3mm, but only if the sky conditions will allow it, (i.e. no bubbling of the atmosphere), otherwise that stays at 6mm too. I have and use an unbranded 6mm LER/UWA. I have a tried a Revalation Astro 6mm Plossl and I found this to be a bit of a let down, due to tight eye-relief. 

Below is the apparent field of view [AFOV] for each of the eyepieces: 

• eyepiece:          AFOV:
• Radian              60deg
• Ortho                45deg
• Nagler zoom    50deg
• LER/UWA          66deg
• Plossl                50deg

I also use the eyepieces as per my signature with the ETX.

[Rob]

I've had a ETX 125 OTA and Skymax 127 in previous kit.. really nice easy to use capable pieces of kit. I do miss them. However cooling is everything with these little beauties!

Rob

[RT65CB-SWL]

On 14/05/2020 at 11:00, Rob said:

I've had a ETX 125 OTA and Skymax 127 in previous kit.. really nice easy to use capable pieces of kit. I do miss them. However cooling is everything with these little beauties!

Rob

I completely forgot about the cooling.

I leave my ETX105 for about 30-60 minutes, (eyepiece end up to the sky), before putting in an eyepiece before viewing, (i.e. leave the end caps off so the internal heat inside the tube can escape). I just pray 🙏 that I don't have bats flying overhead with an IBDM... (irritable bowel disorder movement) 🦇💩 ...not to be confused with an ICBM 😱

Edited May 15, 2020 by Philip R

[John]

If you point the scope downwards the optics are less exposed to passing birds and bats and the warm air in the tube, which should rise, can escape out through the rear port of the scope and out through the diagonal if it is the mirror type and left uncapped.

 

 

 

[JOHN BENNETT]

Well guys I'm overwhelmed with your response and so quickly too. Thanks a lot.

There are a few follow up points your replies raise and I will deal with them in turn

Firstly I will definately check the planetary imaging thread, thanks for that and have a look at specific cameras for planet photography ( though having just invested in my kit I'm not sure I will get away with it ! )

Cooling time is not a particular issue with me as I'm lucky enough to live in a sub tropical climate close to the ocean although generally I do set up some time before dark. I also have made a dew cover

I think the main question I have relates to the eyepieces mentioned in your replies. The use of 6mm and 7mm EP's gives 187x and 216x with no barlow. Is this because the barlow has a detrimental effect on image brightness and is it better to use the EP alone ? Also I note there is mention of some pretty expensive pieces using six or 8 elements with wide AFOV and reasonable eye relief. What particular EP was used for the photos of the moon and Saturn? The Skywatcher kit included a 10mm EP no doubt of dubious quality ( they sell for $10 in OZ ). Which suggests maybe I should consider investing in a quality EP such as the Baader Hyperion 8mm or a Luminos both of which provide wide FOV and about 20mm eye relief. In Australia these cost approx A$200. The Luminus has an adapter for direct connection to the T ring which would be a useful asset. I realise I am jumping ahead a bit but I like to research the issues ahead of time

Any comment on this would be appreciated 

 

 

[Cosmic Geoff]

5 hours ago, JOHN BENNETT said:

I think the main question I have relates to the eyepieces mentioned in your replies. The use of 6mm and 7mm EP's gives 187x and 216x with no barlow. Is this because the barlow has a detrimental effect on image brightness and is it better to use the EP alone ? Also I note there is mention of some pretty expensive pieces using six or 8 elements with wide AFOV and reasonable eye relief. What particular EP was used for the photos of the moon and Saturn? The Skywatcher kit included a 10mm EP no doubt of dubious quality ( they sell for $10 in OZ ). Which suggests maybe I should consider investing in a quality EP such as the Baader Hyperion 8mm or a Luminos both of which provide wide FOV and about 20mm eye relief. In Australia these cost approx A$200. The Luminus has an adapter for direct connection to the T ring which would be a useful asset. I realise I am jumping ahead a bit but I like to research the issues ahead of time

Barlow: your scope has a long focal ratio, so the use of any Barlow will tend to be overkill.  (I don't use one with my 127mm Mak). You can reach the highest useful magnification by using eyepieces of practical focal lengths.  For the same reason, while you could use expensive multi-element eyepeices, you will find that particularly at longer eyepiece focal lengths, inexpensive Plossl eyepieces will work pretty well.  The 10mm Skywatcher eyepiece is unlikely to be of good quality though, and should be upgraded.

Let's be clear: you do NOT use an eyepiece for serious planetary astrophotography. Instead, the planetary video camera replaces the eyepiece.   In general, a DSLR is not used for planetary imaging, and planetary cameras have small sensors and high video frame rates.

[Ags]

I do not use a barlow with my Skymax 102  because you already get high magnification (130-200x) using an eyepiece in the 7 mm to 10 mm range. On screen in the FOV calculator the planet looks small but when you have it in the eyepiece you will see that it is richly detailed and nothing like the dot you see on your screen. You have to remember that your telescope only gathers a fixed amount of light, and when you add a 2x barlow you are making the image 4 times fainter. When you look at a bright blue sky, do you see dots floating in your field of vision? If yes, you will see those same dots obscuring the planet when you use a very high magnification. 

For my pictures of the Moon and Saturn, I used a special astronomy camera (ZWO ASI 178 MM). That costs more than the telescope but you can buy comparable cameras (with a 30% smaller field of view) for less than half the price - and there are always second-hand bargains going. No eyepiece was involved - I inserted the camera in the diagonal instead of an eyepiece. For the Saturn picture, I also used a filter wheel and RGB filters to build a color image as my camera is monochrome.

You mentioned Hyperions. I used to use a Hyperion 17 mm with fine tuning rings that gave me the options of 13 mm and 9 mm with the same eyepiece. In a Skymax 102 the hyperions are lovely eyepieces especially for planetary viewing. I had 3 eyepieces in the 9-10 mm range and the Hyperion with fine tuning rings definitely gave the best view. I sold my Hyperions when I got a different scope - I had a "fast" F5 Newtonian for a while and the Hyperions didn't give a good image there. I now use Explore Scientific 82 degree eyepieces  which are in the same price bracket as the Hyperions but have a better field of view and they work in almost all scopes equally well. The Hyperions were a little more comfortable to use though!

Edited May 15, 2020 by Ags

[Geoff Barnes]

Sorry for being off topic but I noticed you had 999 "likes" @Cosmic Geoff so I took the liberty of getting you the 1000! 👍

[Cosmic Geoff]

2 hours ago, Geoff Barnes said:

Sorry for being off topic but I noticed you had 999 "likes" @Cosmic Geoff so I took the liberty of getting you the 1000! 

Thanks!

[RT65CB-SWL]

Using a 2" SCT star diagonal can make a difference too. That is what is shown in the image of my first reply; especially with TeleVue Nagler e/p's, (I am not bragging, but I have the 13mm 'type 1 & 6'), though you will need to get one of these adapter rings, (image below), to use SCT accessories and screw it on to the rear threaded port.  

<--- This particular one is from www.scopestuff.com

As mine is a Meade ETX105, it is a different design, (though the principle remains the same), and it enables me to attach and use my other SCT accessories.

As others have said; I too do not use a Barlow lens. That said; I may try it, with just a 1.25" nosepiece adapter attached to a T-ring and DSLR or digital compact camera. I also have a 1.6x magnifier which screws in to the e/p nosepiece barrel to give a bit more power. 

Edited May 16, 2020 by Philip R

[JOHN BENNETT]

Great info from you all - thanks. It clears up what I believe turns out to be my main misunderstanding, quote "It seems pointless going to shorter focal length EP's" I was relying on the Barlow to provide the shorter FL but had read of the fainter images, an especially important point with the smaller aperture of the 102. Now I see the sense in using the shorter FL EP. In any case the barlow which came with the kit is nothing special and I was considering upgrading it but am better off investing in a decent EP with good FOV and eye relief. The 8mm Baader Hyperion appeals which is substantiated by our friend in the Netherlands. Baader specifically mentions they perform best in "slow" scopes such as mine. I'm not clear on their 'fine tuning rings' feature but will find out.

At some future time I may replace the star diagonal if considered worthwhile. The 2'' SCT with 1.25' adapter mentioned sounds interesting - would this then accept 1.25' eyepieces ?

Can't afford a planetary camera at present - will mess about with the Nikon ! 

Thanks for your help fellas  All the best

  

[RT65CB-SWL]

11 hours ago, JOHN BENNETT said:

...At some future time I may replace the star diagonal if considered worthwhile. The 2'' SCT with 1.25' adapter mentioned sounds interesting - would this then accept 1.25' eyepieces ?...

  

Yes! - they do include a 2"-1.25" reducer so you can use 1.25" e/ps's and accessories.
I will PM you a larger image of the one I included in my earlier reply.

Edited May 16, 2020 by Philip R

[JOHN BENNETT]

Thanks Phil. It seems to me owning an astronomical telescope is like owning a boat - " a hole in the water you keep throwing money into" ! I have to learn to be patient and consider the dielectric diagonal, planet camera etc later.

In the meantime if I am serious about getting the best out of my Mak 102 I must replace the kit eyepieces. I have researched the Hyperion 'Fine Tuning Rings' and it suggests the 13mm eyepiece would be a better choice. With a 14mm FTR it provides 10.8mm, with a 28mm FTR 7.1 and with both 8.1mm. On top of that by unscrewing the negative lens it converts to 22.9mm. I already have a reasonable 32mm Plossl for target purposes and a 15mm Plossl. I can't see I need anything else. Three eyepieces, two FTR's and no barlow ! A great result. If any of you gurus can see a flaw in this please let me know. Thanks for all your help guys. Avagooday JB 

 

[Ags]

Having used the FTRs (I had the Hyperion 17, the rings giving 13, 11 and 9) and I wouldn't change rings in a session, I would set the EP to what I wanted for the whole evening. They are a bit of a fiddle in the dark.

[John]

Without the lower lens group in place the Hyperion does indeed become a ~22mm eyepiece. Unfortunately it's not a very good one though.

 

[Ags]

Yes - tried it once with my 17 mm - I didn't like the view at all. The view with one, two or the FTRs was excellent however. I would go for the Explore Scientific line these days as the Hyperions are only good in slow scopes.

[ScouseSpaceCadet]

For planetary observation with the Skymax 102 there's absolutely no need to go spend crazy on expensive wide field eyepieces, or barlows.

With a Skywatcher 1.25" dielectric diagonal the Skywatcher UWA 58° 6mm eyepiece, pushes the instrument past its theoretical max of 204x, to 216x, producing a sharp image. I've also tried a 4mm TMB clone for lunar viewing at 325x and it was OK. Not fantastic, but OK.

However, I wouldn't suggest pushing the scope past max. magnification because there are other factors to consider, it may be sensible to aim for just under max. Either a 6.5 or 7mm long eye relief eyepiece.

The Explore Scientific 6.5mm LER 52° eyepiece will give 200x and isn't massively expensive.

https://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-52-ler-series-eyepieces.html

Edited May 19, 2020 by ScouseSpaceCadet