Ricochet

37 minutes ago, Franklin said:

Lol......

Yes, been there, bought the T-Shirt etc....

I have pairs of LV20mm and LV10mm for when the bino's come out to play. I think doubling up the LVW's would a) create serious balance issues and more importantly b) put me on a diet of bread and water for the foreseeable future 😂.

Oh yes, I didn't mean that you should buy a second set of LVWs, but that you would need a whole other set of (smaller) eyepiece pairs.

33 minutes ago, Mike Q said:

How old is yours.  I have not noticed any internal reflection in mine, but i have not used it a ton and i may not have noticed it as of yet 

I've no idea. I bought it second hand perhaps 5 years ago. However, I would hazard a guess that there's a 99.999% chance that the same issue exists in all examples and that the reason I noticed it was down to a) Using eyepieces with absolutely top notch coatings, transmission and baffling and b) Becoming quite picky about light scatter issues as I've become a more experienced observer.

1 minute ago, Franklin said:

I don't need a barlow or anymore eyepieces for that matter.

Until you buy a binoviewer.

1 minute ago, Mike Q said:

Both are made by JOC i believe

Yes. The Orion is the old body style design that JOC used to provide to Meade (now owned by Orion) and the ES is the new body style. I've got a Meade branded one and there are some reflections from the plastic inner wall between the two groups of lenses. Flocking this section will improve the contrast.

24 minutes ago, PeterStudz said:

the rubber is a bit too solid for my liking with a spectacle level pressed against them. 

Yes, this is why I said the eye relief is not really enough. I found that they pressed my glasses into my face which was not comfortable. For people with slightly less deep set eyes perhaps the eye relief is adequate.

16 minutes ago, bosun21 said:

I always took the red ring to be the secondary mirror that’s why it’s centered in the focuser tube. and can show the reflection of the primary mirror. And the central dark area is a reflection of the cap or the poorly reflective surface of the cap/Cheshire. If I’m wrong please explain to me how you get a secondary shadow please.

When you collimate the telescope you do so with the front cap off. Light comes into the telescope, reflects off the primary and secondary and into your eye. This is why the primary appears to be bright - the large white area in the image. In the centre of the opening at the top of the telescope you have the secondary mirror and spider which blocks the light entering the tube. This is why there is a large dark area in the centre with four dark spider vanes shown horizontally and vertically. The reflection of the cap is the small bright area in the centre. Inside this you will see the dark central spot which is the hole in the cap (where there is no reflective material) and also a dark deflection of the primary doughnut.

Here is a photo taken through a collimation cap. It is too dark around the outside to see the edge of the secondary mirror so everything you are seeing is reflections. Working from outside in you have:

1. Bright reflection of primary with three shadows of mirror clips. If you look carefully at the left hand side you can see if goes slightly flat where the focuser drawtube just grazes the light path.
2. Dark shadow of the secondary mirror with four spider vanes. You can note that the horizontal spider vanes are not quite parallel and you can see screw heads protruding from the spider on the left, bottom and top (just!) sides. You may also notice that this shadow is not actually round because the central boss of the spider is large and the mirror is offset so there is a crescent of shadow to the left that is the central boss not the secondary mirror itself. In a different brand telescope with a smaller boss you would see only the shadow of the secondary and the shadow should be round (but offset).
3. Bright central area. This is the reflection from the reflective surface on the underside of the collimation cap
4. Dark ring. This is the reflection of the doughnut in the centre of the primary.
5. Dark dot. This is the shadow of the hole in the centre of the collimation cap.

If you can afford it I would target a 24mm 68° eyepiece for your lowest power/finder as this will give a darker background sky than a 32mm Plossl whilst showing approximately the same true field (5mm exit pupil vs 7mm). This will have the most effect if your skies suffer from any light pollution. Depending on your budget the options suitable for an f5 telescope are the Ultra Flat Field (UFF), of which I believe the Stellalyra is the current cheapest branding, the Explore Scientific 68°, or the Televue Panoptic. 

Alternatively, in a dark sky location a 7mm exit pupil might be ok in which case the 30mm UFF might be a better low power option if it is within your budget and your 150p has a 2" focuser.

As suggested above, the 12/8/5mm Starguiders work well at f5 and can be had relatively cheaply, but do not have enough eye relief if you need to wear glasses while observing due to astigmatism. An idea of your budget would be useful as other suitable eyepieces would be the Nirvanas, Explore Scientific 68/82/92°, UFFs, Vixen SLV, Baader Morpheus, Pentax XW, Televue (all ranges) and there is a significant cost difference between the cheapest and most expensive options.

10 hours ago, bosun21 said:

the reflection of your cap or Cheshire should be offset towards the open end of your scope

It may appear that the cap reflection is offset away from the primary but in fact it is the shadow of the secondary which will appear offset towards the primary mirror. The reflection of the cap and the central hole should be perfectly centred, with the hole appearing as a dot inside the also centred primary doughnut.

This image from @Spile's guide shows it best. The central dark spot, light circle and red/green/blue circles are all concentric and the dark dot sits exactly under the centre point marked by the cheshire crosshairs. Only the larger dark circle (secondary shadow) is offset from the centre.

One of these? There is there is manual for new ones in the downloads section of the linked page. 

29 minutes ago, Chris said:

😄 I'm thinking Ursa Major 80mm f/6.3 Table top Dobsonian verses the Mercury 707?

https://www.firstlightoptics.com/ursa-major-telescopes/ursa-major-80mm-tabletop-dobsonian-telescope.html

https://www.firstlightoptics.com/beginner-telescopes/sky-watcher-mercury-707-az-telescope.html  

Timing my 3 kids whilst they set them up, find objects and focus. Followed by a vote on ease of use and views seen. 

 

 

I was thinking more along the lines of a Skywatcher mercury or the celestron starsense 70az with a yoke mount vs say the Astromaster 70az and 70eq but yeah, throwing a similarly priced mini-dob set up into the mix would be something that I am sure would benefit all those parents who in the run up to a birthday or Christmas ask similar questions to the one posed in this thread. As adults we try to give our opinions on what we think or what we have seen but having kids give their views is probably a better perspective. 

14 minutes ago, Chris said:

What do others think of the Mercuary 707's yoke mount?

I think it sounds like time for a 70mm f10 mount comparison video. 

Of the two initially suggested telescopes I would go for the 70mm Starsense refractor. These slow, relatively long focal length refractors will probably give sharper lunar and planetary images than the fast, short focal length newtonians, especially if a spherical mirror is used. On deep sky there probably isn't a lot between a 70mm frac and a 76mm newt, if anything the frac probably edges it here too. If you know that your daughter much prefers stars to the moon and planets then stepping up to at least a 100mm mini dob is probably as good or better than the 70mm frac. However, the starsense system has been getting good reviews and will make finding things a lot easier if you have a suitable phone that can be donated or leant for each observing session. 

It's broken and needs replacing. While you're getting it replaced I would advise upgrading to the Premium Stellalyra one which is 1.25" for almost the whole height of the cheshire so you can better match the bottom of the tube to the apparent secondary size and which has much better crosshairs. The thin wire used in the cheap ones has a tendency to stretch and deform if anything comes into contact with it. The angled face/peephole is probably more accurately positioned as well, even comparing examples where they're not loose and spinning around.

What eyepiece will he be using as a finder? If he's only using 1.25" eyepieces he will be limited to ~2.2° so the question is whether he thinks that is wide enough to find things with. If it isn't, which would be my initial assumption, he will want a RACI finder in conjunction with an RDF. If he can get a satisfactorily wide view through the eyepiece then the optical finder can be omitted and the RDF will suffice. 

For comparison with my dob my widest field is 1.8° and I use a 9x50 RACI and Telrad. At the other end of the scale with my 72ED I can get 3.9° (1.25") and so only need an RDF. 

41 minutes ago, JD Astro Novice said:

let me know if that’s what I should be seeing

If you adjust the focuser to move the Cheshire out a bit it might show the other clips and then maybe a bigger gap on the left (so the secondary should move up the tube by shortening the centre screw). I can't make out exactly where the edge of the Cheshire is though to be sure. 

However, I think for a first time collimation that is a cracking effort and you should congratulate yourself for a job well done and get out under the stars and enjoy using the scope. 

I always found a 7mm eyepiece you've quite a good match for typical uk atmospheric conditions. The Celestron X-Cel LX is a good, sharp eyepiece. If you want to spend more then the Pentax XW or 6.5mm Baader Morpheus would be good choices. All these lines have a 4.5 or 5mm option as well for even higher power that should be within your scope's capabilities, but not always allowed by the atmosphere. 

Alternatively, I prefer to binoview for lunar/planetary but this will first require buying a binoviewer and finding barlows or gpcs that allow it to focus before choosing eyepiece pairs. The Baader Max bright 2 with newton gpc might be an option but you will need to compare the infocus requirement listed in its manual and compare it to how much infocus you have on your telescope from the single eyepiece focus position. 

8 minutes ago, toofaruphill said:

If nothing there  fits I have a  lathe , no problem

You don't need that. Fit the diagonal into the back of the telescope and the eyepiece into the diagonal. Turn the focuser knob until you get to focus. If you go all the way to the end and it won't turn any further you went the wrong way so turn it the other way until you find focus. Try in the daytime. If you can focus on something reasonably far away see which way you need to turn the knob to focus on something a bit further away. The stars are even further away so that is the direction you will need to turn the knob to focus at night.

Which exact Mak do you have? Is the focuser a knob in the back plate or a separate focuser? If it is the knob directly on the back plate it will have loads of focuser travel and you just need to turn it more to find focus.

Are these the white Bresser "Messier" telescopes with the black hexagonal cross section focuser? If they are Bresser have a tendency to package the required focuser extension piece separately. It goes between the part with the hexagonal cross section and the eyepiece/diagonal clamp. There is a grub screw that has to be loosened to allow the clamp to be removed. 

9 hours ago, JD Astro Novice said:

This still only results in an off centre alignment with the secondary mirror through the Cheshire

Can you explain further what you mean by this comment? In what way is it off centre? If the telescope tube is horizontal with the open end at the left, in which way is the secondary(?) offest? Also, if you can get a photo through your cheshire and upload it here it would help us to advise what you need to do.

9 hours ago, JD Astro Novice said:

Even with this and then alignment of the primary I managed to get a pretty perfect view of the moon tonight with great detail so is it really out of collimation?

It might be out, without photos I can't really say, but as you have found, collimation doesn't have to be perfect which is good news as it means that you don't have to worry about it too much. Sure, to squeeze every last drop of performance out of the scope it needs to be good but if you have the choice between tearing your hair out for 99.9% performance and not worrying about it and getting 90% go with the later. No one got a spot on collimation the first time they tried it and each time you give it another go you'll get slightly better at it. In the meantime just enjoy using the telescope.

9 hours ago, JD Astro Novice said:

I then get thrown when looking at a bright object like Mars and when I focus right out it is clearly not aligned with quarter of the primary out of shot. 

Is Mars centred in the field of view when you do this? If it is could you roughly draw what it is that you see?

10 hours ago, JD Astro Novice said:

I think I may need to completely reset and tighten everything and then start again?

Not completely. You've said your spider vanes are equal lengths so don't touch those. The steps you want to use are:

1. Adjust centre screw (and also loosen/tighten collimation screws to match) to get secondary centred under focuser. If you've got your scope horizontal this means you want the same space between the edge of the secondary mirror and the wall of your cheshire to both the left and right.
2. Adjust the collimation screws to get the mirror appearing to be circular. As above. you may find it easier to back of the collimation screws so you can use your hand to hold the mirror in the correct position and then tighten them up. You may also need to use these to move the mirror up/down when viewed through the cheshire. 
3. Adjust the three collimation screws so that the cheshire crosshair points at the doughnut in the centre of the primary. If this messes up step 2, don't worry about it and move on.
4. Adjust the primary mirror so that the black dot created by the peep hole in the centre of the cheshire is centred in the doughnut on the primary mirror.

Personally, I think that you should concentrate on choosing the scope that you want rather than thinking of which accessories you can also buy. Accessories tend to be cheaper and so it is much easier for you to save up again in the future for an accessory than it is to save up again for a whole new scope because you didn't buy the one you really wanted to save money now. 

5 hours ago, spacedobsonian said:

Ursa Major 102mm set:

Ursa Major 102mm dobsonian:

https://www.firstlightoptics.com/beginner-telescopes/ursa-major-102mm-tabletop-dobsonian-telescope.html

The good thing about dobsonians is that you tend to get a very stable base for a relatively cheap price. However, with these table top dobs you need something stable to put them on at your observing location so the eyepiece is raised to a reasonable height. If you are going out in your garden or to a local park where there are nice sturdy tables you'll be fine, but in a featureless field or on the side of a hill you will probably want a tripod.

5 hours ago, spacedobsonian said:

Sky-Watcher StarQuest-130P f/5 Parabolic Newtonian Reflector set:

Sky-Watcher StarQuest-130P f/5 Parabolic Newtonian Reflector (Only a telescope, no accesories for this one because the budget is tight!) : 

https://www.firstlightoptics.com/sky-watcher-starquest/sky-watcher-starquest-130p-f5-parabolic-newtonian-reflector-telescope.html

Sky-Watcher Explorer 130 (EQ-2) set:

Skywatcher Explorer 130 (EQ-2):

https://www.firstlightoptics.com/reflectors/skywatcher-explorer-130.html

I would prefer either of these to the first option due to the increased aperture. Particularly when observing DSOs, aperture is king and jumping from 102 to 130mm is a significant jump. If I was looking to buy myself a small Newtonian today, I would probably be looking at a 130mm scope just for that extra bit of light grasp over the smaller options. Of the two I think I would prefer the f5 parabolic scope but I do not know for sure how the two mounts compare. I think they are pretty similar but I notice that the 130p on EQ2 is the more expensive choice.

@Chris did a couple of videos on the Starquest 130p so I would suggest watching those and seeing what he thought of it:

Starquest 130p First Impressions

Starquest 130p Review

5 hours ago, spacedobsonian said:

Sky-Watcher Startravel 80 set:

Sky-Watcher Startravel 80 OTA:

https://www.firstlightoptics.com/startravel/skywatcher-startravel-80-ota.html

Tripod:

https://www.firstlightoptics.com/tripods/fotomate-vt-6006-heavy-duty-2-way-tripod.html

I don't really like this suggestion and it is mostly because of the tripod. I don't think that tripod looks anywhere near stable enough for astronomy and with any alt-az head where the telescope is mounted above the pivot, rather than to the side of it, there is a tendency for the telescope to drift upwards as the head is unable to hold the weight without extreme tightening. Aside from perhaps being easier to store and transport I don't see what there is to gain over the Startravel 80 AZ3 bundle which I suspect would be much better for astronomical observations, especially with the slow motion controls that should allow you to track without loosening the axis tightness.

However, there are a couple of other refractor options within your budget, namely the Evostar 90 on either AZ3 or EQ2 mounts:

Evostar 90 AZ3

Evostar 90 EQ2

The Evostar 90 has a little bit more aperture than the 80, but most importantly it has double the focal ratio, so chromatic aberration will be greatly reduced making it a superior scope on lunar and planetary targets. I think I would go for a Evostar 90 EQ2 over the ST80 if it were my choice.

If you prefer DSO targets then there are a couple more refractor options slightly over your budget:

Evostar 90/660 Pronto

Startravel 102 AZ3

The first will give better correction than the ST80 and a wider field of view than the 90/900 Evostar.

The ST102 will give a good jump in light gathering over the ST80 for better DSO performance. However, I think the 130p will probably be better for both DSOs and planetary.

The centre screw is for moving the secondary up and down the tube so that you can have it directly under the focuser. All other adjustments are via the three collimation screws. These are the ones you need to adjust. You may find it easier to back all three off, use your hand to hold the secondary stalk, manually turn/angle it to the correct position and then tighten the collimation screws. This is not the easiest thing as you need to be looking down the Cheshire with two hands down the front of the scope. 

1 hour ago, stressballs1 said:

Hi. I am looking at a Sky-Watcher Heritage 150P Flextube Dobsonian. I already have a Celestron 4se eq mount. As the Dobsonian has a rail to fix onto a mount, would the mount be strong enough to handle the tube and dslr(nikon D7000)?

Forget the mount, it's the heritage focuser (not) holding a dslr that I would be worried about. I'm sure you would be much better off buying one of the standard suggestions of a 130pds or 80ED. 

As above, eyepiece sets are generally not a good deal as you end up paying for extra eyepieces that you don't need. I would suggest that you look at buying the following eyepieces:

1. A finder eyepiece, typically with an exit pupil of around 5mm. For your f6.92 scope that gives 6.92x5 = 35mm. The best match here is a 32mm Plossl (with an apparent field of ~50°) which gives the widest true field possible for a 1.25" eyepiece. Any brand in your budget will a good choice here.
2. A main DSO eyepiece with an exit pupil in the range 2-2.5mm, so an eyepiece in the range of 14-17mm. I would recommend that most of your budget goes on this eyepiece as it is the one you will probably spend most of your time using. I don't recommend the 68° 15mm from your second link as I've used one and it was terrible. The rest of the range are supposed to be better though. A 15mm Starguider (under any branding) would be a nice comfortable choice. If you can stretch to it the 16mm from what we know as the OVL Nirvana range would be a great choice. At the cheaper end of the scale a 15mm Plossl would should still have a comfortable enough eye relief whilst still giving a good view.
3. A lunar and planetary eyepiece. Again, I'm going to suggest something that might be above budget, and that I haven't used, which is the new SVBony 3-8mm zoom. Early reports are quite promising and it would give you the ability to dial in the exact magnification that gives the best view for each object. You will probably only need the 5-8mm section with your telescope but having that extra magnification if you want to use it won't hurt.

The good thing about these not being a set is that you don't have to buy all of them at once, so where they are over your budget you can buy one or two now and then save up for the rest at a later date. Personally, I think I would start with 1 and 2 and then save for 3, although Jupiter and Mars are quite well placed at the moment.

Thanks, Louis. I should have known you'd have something from that line.