Is the advice "The HEQ5 is the entry point to AP" just plain wrong?

[ollypenrice]

4 hours ago, wuthton said:

This is exactly my point... for me.... IMO... the cheapest way to a great astrophotograph is spending your money on pixel scale, not guiding accuracy. It's heresy I know but I believed it with CCDs and CMOS has just cemented my opinion.

I really, really believe the default advice for newcomers to this fabulous hobby should be "keep your focal length short and buy a good camera"  NOT  "You need a HEQ5". 

But that is, consistently, the advice usually given. It's certainly what I always recommend along with a priority order of mount-camera-optics. I won't budge on putting the mount first. It's also cheaper to image at a coarse pixel scale than a fine one, so it might be more accurate to say, 'Avoid spending your money by choosing a short focal length.' For once cheaper is better because it would be silly to start imaging at the hard end of the focal length scale.

Why won't I budge on the mount coming first? Partly because the 'round stars test' is oft-repeated but wrong. It tells you only that your tracking errors are about equal in RA and Dec yet it tells you nothing whatever about how large they are. It doesn't matter what your camera and lens are: if they're moving relative to your target the image will be blurred. 3.5 arcsecs per pixel meets your low res imaging requirement. The periodic error of an unguided HEQ5 could easily be 10x that. We must come back to the simple rule that guide RMS in arcseconds must be half or less of that of the imaging scale.

Olly

[vlaiv]

4 minutes ago, Chris said:

Around 1k all in for everything, give or take : )

I'll counter that thought with how likely is a beginner to keep a portable rig if they upgrade to something larger and more capable? 

E.g. I have a Star Adventurer for portability and widefield, and a more serious rig in the obsy. 

What if they drop 2k plus on an HEQ5 pro based rig and decide it's not for them. 

We can spin this several different ways, but I don't think we can find a black and white answer to this because 2-3k is pocket change to some but an absolute fortune to others, and some will love AP and go deep into the hobby and for others an imaging rig might end up collecting dust. 

 

 

 

I agree and I think it is a pity there is no single "obvious/sensible" answer to this question - setup that is relatively affordable and "can do it all" (to an extent obviously).

Above is based on what I perceive to be common beginner question when looking for starter gear in this hobby.

So far I've gathered that most people do want to be able to do some visual, want to do some "mixed meat" astrophotography - so basically to try a bit of everything - some lunar/planetary, some DSO - a bit of galaxies, a bit of wide field and so on, and their budget is £300-500 most of the time. Obviously, there is no solution to that equation, but what is the answer that comes closest?

Something needs to be sacrificed, but what? And if there are several options - then how to best present pros and cons for people to choose themselves?

This is somewhat off topic but I guess it is related. I think that start into "serious" AP (one that can handle most of bits of AP and do it good) - is still those requirements that I listed (10Kg+, 1" RMS, ...,.).

Here is another question. Which one would you recommend to novice in 1k category:

70mm ED scope + flattener + Az gti mount with mods + DSLR

versus

manual eq5 + single RA motor + 130PDS + SW 0.9 CC + DSLR

[vlaiv]

2 minutes ago, ollypenrice said:

3.5 arcsecs per pixel meets your low res imaging requirement. The periodic error of an unguided HEQ5 could easily be 10x that.

That sort of paints a bleak image, doesn't it?

In reality - P2P error of say 35" is spread over 638 seconds, so it takes about 300s to go those 35" (full cycle is a Hobbit's tale - there and back again ), or about 1" per 10 seconds (give or take). Somewhere along the curve things will be slower, and somewhere faster - so at least 50% of subs of 30s exposure length will have that "RMS = half of imaging resolution" thing even unguided.

This was taken on HEQ5 with planetary type camera - unguided. I don't remember exposure length, but it was something like 30s-1m, not longer than that. It is 4.6"/px (it was taken with F/7.6 scope and tiny sensor in heavy LP  - not the best combination). Above is 100% zoom - just to show that stars are nice and round. I don't think I've discarded any subs.

[ollypenrice]

6 minutes ago, vlaiv said:

That sort of paints a bleak image, doesn't it?

In reality - P2P error of say 35" is spread over 638 seconds, so it takes about 300s to go those 35" (full cycle is a Hobbit's tale - there and back again ), or about 1" per 10 seconds (give or take). Somewhere along the curve things will be slower, and somewhere faster - so at least 50% of subs of 30s exposure length will have that "RMS = half of imaging resolution" thing even unguided.

This was taken on HEQ5 with planetary type camera - unguided. I don't remember exposure length, but it was something like 30s-1m, not longer than that. It is 4.6"/px (it was taken with F/7.6 scope and tiny sensor in heavy LP  - not the best combination). Above is 100% zoom - just to show that stars are nice and round. I don't think I've discarded any subs.

It's not intended to be bleak but to point out the nature of the problem. The (nice) photo above is of the brightest deep sky object in the sky, the Trapezium region of Orion. It's the only DS object I've ever imaged which required a maximum exposure time of around ten seconds. Its nearest rival is the large blob in the middle of M31, which isn't worth imaging anyway! 

Olly

Edited January 29, 2022 by ollypenrice
Typo

[iantaylor2uk]

21 minutes ago, ollypenrice said:

But that is, consistently, the advice usually given. It's certainly what I always recommend along with a priority order of mount-camera-optics. I won't budge on putting the mount first. It's also cheaper to image at a coarse pixel scale than a fine one, so it might be more accurate to say, 'Avoid spending your money by choosing a short focal length.' For once cheaper is better because it would be silly to start imaging at the hard end of the focal length scale.

Why won't I budge on the mount coming first? Partly because the 'round stars test' is oft-repeated but wrong. It tells you only that your tracking errors are about equal in RA and Dec yet it tells you nothing whatever about how large they are. It doesn't matter what your camera and lens are: if they're moving relative to your target the image will be blurred. 3.5 arcsecs per pixel meets your low res imaging requirement. The periodic error of an unguided HEQ5 could easily be 10x that. We must come back to the simple rule that guide RMS in arcseconds must be half or less of that of the imaging scale.

Olly

Although the advice that guide RMS in arcseconds must be half or less that of the imaging scale is often stated, I think it is a bit too conservative.

My reasoning is as follows: Let's say guide RMS is 1" - then that would suggest that you need to be imaging at 2" or greater. However, to get a guide RMS of 1", if RA and DEC errors are equal, then the RA and DEC RMS would only be around 0.71", so I would have thought you would still be OK imaging down to a main camera scale of 1.4". Also, all of this ignores the effects of seeing, which could easily be 2-3". 

[ollypenrice]

3 minutes ago, iantaylor2uk said:

Although the advice that guide RMS in arcseconds must be half or less that of the imaging scale is often stated, I think it is a bit too conservative.

My reasoning is as follows: Let's say guide RMS is 1" - then that would suggest that you need to be imaging at 2" or greater. However, to get a guide RMS of 1", if RA and DEC errors are equal, then the RA and DEC RMS would only be around 0.71", so I would have thought you would still be OK imaging down to a main camera scale of 1.4". Also, all of this ignores the effects of seeing, which could easily be 2-3". 

OK but, even if this is entirely correct, what does it say, in your view, about the HEQ5 being the minimum mount?

Olly

[iantaylor2uk]

I would say a HEQ-5 is a good starter mount if you are imaging in the 500-800mm focal length range. If you are happy with shorter focal lengths (135-300 mm) to start with, I would advise to go with a tracker mount, and get used to astrophotography and see if you like it before taking a deeper dive in. 

[malc-c]

45 minutes ago, Chris said:

We can spin this several different ways, but I don't think we can find a black and white answer to this because 2-3k is pocket change to some but an absolute fortune to others, and some will love AP and go deep into the hobby and for others an imaging rig might end up collecting dust. 

And I think that really wraps up the thread... 

We've been generalising things, where in reality it's really down to each individual case.  I've had times in my life where the income was good and thought nothing about spending £600 on quality tongue and groove shiplap to cover the observatory, but now in my current circumstances watch every penny...

[vlaiv]

Well, that half resolution recommendation is just rule of the thumb.

A bit more precise formulation would be like this:

- star FWHM in the image depends on several factors - seeing, aperture size / telescope spot diagram and guide performance.

- sampling rate should be FWHM / 1.6

here is example for 80mm diffraction limited telescope and 2" and 3" second seeing and 1" and 1.5" guiding RMS

2" seeing, 1" RMS = 3.39" star FWHM or 2.12"/px

2" seeing, 1.5" RMS = 4.295" star FWHM or 2.68"/px

3" seeing, 1" RMS = 4.06" star FWHM or 2.54"/px

3" seeing, 1.5" RMS = 4.84" star FWHM or 3"/px

It is better to image in 3" seeing with 1" RMS than it is to image in 2" with 1.5" RMS. Why is that?

Because of units. RMS and FWHM are not the same and there is relationship that states FWHM = 2.355 * RMS (for gaussian curve).

For this reason 1" difference in FWHM is about the same as 0.5" change in RMS (even a bit smaller in this case).

 

 

[malc-c]

14 minutes ago, iantaylor2uk said:

I would say a HEQ-5 is a good starter mount if you are imaging in the 500-800mm focal length range. If you are happy with shorter focal lengths (135-300 mm) to start with, I would advise to go with a tracker mount, and get used to astrophotography and see if you like it before taking a deeper dive in. 

Again related to the issue of so many variables, we're comparing apples to oranges as you can image a target with a 500mm telephoto lens, or bolt a camera to a 1m focal length  f5 200P reflector... or a  1m focal length f8 Evostar...   A lot of the time the targets, portability and how the newbie intends to image is not forthcoming

Personally if using a 200m reflector or 120mm refractor then the HEQ5 is the minimum requirement mount wise.

[malc-c]

1 hour ago, Chris said:

I'm not sure how many people would recommend a several Kilogram camera with a huge megapixel count to a beginner? 

Your 400D weighs around 500g and has about 10MP.

My Fuji XT1 is similar to this too.

E.g. a Canon 400D with ED72 plus 0.8 flattener would give you 3.5"/seconds ish. 

To me this seems like a reasonable pixel scale and camera for someone starting out. (although the 450D would be better with live view)  

The AZ GTI in EQ mode can handle a the above, and so can the EQM35. 

 

 

Maybe I miss-phrased that.

What I was meaning was in regard to the statement made about recommending large megapixel cameras as a priority over the mount.  The nearest  lightweight dedicated CCD astro camera I can see around the same price as an HEQ5 is  the ASI 1600MM - with 16mp 4/3 sensor.  Now I would be more disappointed if  having spent £950 on a camera it gave me poor results because I was advised to get an EQ3 mount to take a 150p and guidescope rather than a rock solid HEQ5.

As you informed me above, a cheap D400 or 450 (I really wished I had picked up the 450 for its live view, but hey ho !) would give a reasonable pixel count and scale, leaving more money for other equipment like the mount.

[Chris]

2 hours ago, vlaiv said:

Which one would you recommend to novice in 1k category:

70mm ED scope + flattener + Az gti mount with mods + DSLR

versus

manual eq5 + single RA motor + 130PDS + SW 0.9 CC + DSLR

If mainly interested in DSO imaging then the ED70 AZ GTI (with the wedge, counterweight mod, and firmware update) might be the better option because you can get around the lack of a polar scope by plate solving with software, and guiding works well with these setups. You also have the goto to help locate faint objects to image. You can also upgrade to the ASI Air plus to make things easier at some point down the line. 70mm isn't a great deal of aperture for observing or planetary imaging so best kept purely for DSO imaging. 

If they would like to dabble with a bit of everything it's hard to argue with a moderate sized 130pds/150p f/5 reflector on an EQ5 mount with basic drive. These have a bit of aperture for the visual side of things, and with regards to DSO imaging you can start off imaging the brighter DSO's with 30 second exposures, then upgrade to the Synscan goto upgrade or Asterion goto upgrade kit at a later date. 130pds/150p will be relatively good for planetary Lunar imaging and observing, just add a Barlow and planetary cam.   

[adyj1]

3 hours ago, malc-c said:

And I think that really wraps up the thread... 

What I would say is there's general agreement that if you want to do 'serious' AP then the HEQ5 is the most appropriate mount for the money. (You'll also need to learn what pixels-per-arcsecond means 😉) . 

If a beginner suggests they want to 'have a go at AP', then the HEQ5 really needs to be qualified as the sort of option you'd take if you were looking to spend (say) in the region of a couple of thousand on a full starter rig - buy the HEQ5 now and some lesser other kit, then when you upgrade to the quality ota/camera/etc you won't need to upgrade the mount - which is good, as although you'll be looking to spend £1000+ for that next upgrade anyway. With the HEQ5 you'll have had a better beginners experience than if you chose a poor mount because you'll (hopefully) had more consistently good results/experiences with the HEQ5. 

Of course, if your budget is in the thousands as a beginner, good luck to you there's no reason not to mate the HEQ5 with decent kit to start with. 

Again, the recommendation to get an HEQ5 needs to have considered the beginners budget, and explained that there are cheaper options that give acceptable results for beginners (well, not just beginners, tbh, but that is the topic of this thread.).

 

[SamAndrew]

Buy second hand and this hobby doesn't have to cost you anything (especially considering the way prices are going)

The scarcity of HEQ5s on the used market says it all, it's a good investment, you might lose a few hundred if you buy new and then sell it on.

I've owned a lot of scopes; I'd say half of them haven't cost a penny.

[ollypenrice]

I don't think it's for any of us to say what the advice ought to be. What we should do is state our own view and give reasons. That's how forums work. 

Looking back, my own advice has sometimes been mainstream, as in start with the mount - sometimes middle of the road, as in putting camera before optics - and sometimes minority, as in start with mono and filters, autoguide from the start and don't feel obliged to start with a DSLR.  I also try not to post outside my competence. 'I'm not a planetary imager, but...' I certainly hope I've never said that and, if I have, I apologize now! 

Olly

 

Edited January 29, 2022 by ollypenrice
Typo

[ollypenrice]

10 hours ago, Chris said:

I'm probably not the only one to suggest shorter focal length (more forgiving) setups to beginners, and I feel you don't need an HEQ5 at shorter focal lengths/larger pixel scales.

I've personally had bad luck with second hand mounts, it's the one part of an imaging rig I'd recommend buying new. The HEQ5 Pro currently retails for around £950. 

Putting yourself in the shoes of someone starting out it's hard to jump to the suggestion of an HEQ5 pro sometimes when they say I want to do AP my budget is 300 quid.  

You need to find a middle ground

 

 

I hear you, but I bought two second hand mounts which both turned out to be the most reliable items I ever bought. They were Mesus, however.

Olly

[Clarkey]

1 hour ago, ollypenrice said:

I also try not to post outside my competence.

Might as well remove my profile now.....

Edited January 29, 2022 by Clarkey

[900SL]

I keep banging the drum about the Fornax Lighttrack 2 but it's a lightweight tracker I'm never selling.

Portable, super accurate tracking, good for 20mm wide angle Milky Way all the way through to DSO with a WO GT71, unguided 3 - 5 minutes

 I use an ASIAirPro for PA and platesolving to confirm framing, no guiding, no go-to, no PC... 1 arc second tracking 

 

Edited January 30, 2022 by 900SL

[ollypenrice]

14 minutes ago, 900SL said:

I keep banging the drum about the Fornax Lighttrack 2 but it's a lightweight tracker I'm never selling.

Portable, super accurate tracking, good for 20mm wide angle Milky Way all the way through to DSO with a WO GT71, unguided 3 - 5 minutes

 I use an ASIAirPro for PA and platesolving to confirm framing, no guiding, no go-to, no PC... 1 arc second tracking 

 

Have you done a full review on here? I'd be interested to read more, as would others, I'm sure.

Olly

[900SL]

33 minutes ago, ollypenrice said:

Have you done a full review on here? I'd be interested to read more, as would others, I'm sure.

Olly

No but I would be happy to do so Olly. I have a F LT2 dedicated thread here which is pretty quiet   

 

[wuthton]

23 hours ago, malc-c said:

But I can't see that being the case... There's not much point buying a huge mega pixel camera that weighs a few kg and then attaching it to a mount that lacks the fine accuracy and precision to take advantage of that pixels/ mm count the sensor will offer.

If what you mean by huge mega pixel camera is a camera with huge pixels then yes there is a lot of point. At a short focal lengths, high precision mounts make absolutely no difference whatsoever. My trusty, old Atik 314+ and Samyang 135mm has scale of 8.25"/pixel and I'll do the Daz doorstep challenge with that on the cheapest tracking mount you care to name vs a DSLR on a HEQ5.

Edited January 30, 2022 by wuthton
typo

[kens]

Well I guess now, nobody is going to be game to recommend a HEQ5 to this guy  🤣

 

[malc-c]

55 minutes ago, kens said:

Well I guess now, nobody is going to be game to recommend a HEQ5 to this guy  🤣

 

Hence why I asked for more info.... rather than jumping in with both feed 😉

[ONIKKINEN]

12 hours ago, wuthton said:

If what you mean by huge mega pixel camera is a camera with huge pixels then yes there is a lot of point. At a short focal lengths, high precision mounts make absolutely no difference whatsoever. My trusty, old Atik 314+ and Samyang 135mm has scale of 8.25"/pixel and I'll do the Daz doorstep challenge with that on the cheapest tracking mount you care to name vs a DSLR on a HEQ5.

My very first astrophoto was taken with a Canon 550D and a kit lens at 100mm fl piggybacking on an Astromaster 130MD with the motor running. Took 12s exposures and stars were very much round, so i think if the astromaster can handle an 8 arcsec/pixel resolution any mount in the universe can.

Wasn't a good picture of course, but point is at this kind of resolution i doubt you can find a mount that just flat out fails to work.

[vlaiv]

9 minutes ago, ONIKKINEN said:

My very first astrophoto was taken with a Canon 550D and a kit lens at 100mm fl piggybacking on an Astromaster 130MD with the motor running. Took 12s exposures and stars were very much round, so i think if the astromaster can handle an 8 arcsec/pixel resolution any mount in the universe can.

Wasn't a good picture of course, but point is at this kind of resolution i doubt you can find a mount that just flat out fails to work.

Well, interesting thing about mounts and tracking is that tracking error in pixels decreases with declination.

It takes Polaris 24h to move 4° in pixel space (it is about 38.5 arc minutes from NCP and circumference of the circle is 2*r*pi so that is about 240 arc minutes or 4°). If you image at 8"/px - than that is about 450px of motion in 24h or 18.75px per hour, or 1px in 3 minutes.

Even if your mount does not move at all - at that declination and that resolution stars will stay mostly round in 3 minute exposures.

In order to really test your mount - you need to track at meridian and then see how well it behaves (same goes for guiding).